Environmental Impact of the Production of Mealworms as a Protein Source for Humans – A Life Cycle Assessment

The demand for animal protein is expected to rise by 70–80% between 2012 and 2050, while the current animal production sector already causes major environmental degradation. Edible insects are suggested as a more sustainable source of animal protein. However, few experimental data regarding environmental impact of insect production are available. Therefore, a lifecycle assessment for mealworm production was conducted, in which greenhouse gas production, energy use and land use were quantified and compared to conventional sources of animal protein. Production of one kg of edible protein from milk, chicken, pork or beef result in higher greenhouse gas emissions, require similar amounts of energy and require much more land. This study demonstrates that mealworms should be considered a more sustainable source of edible protein.     

Dug1p Is a Cys-Gly Peptidase of the ��-Glutamyl Cycle of Saccharomyces cerevisiae and Represents a Novel Family of Cys-Gly Peptidases

GSH metabolism in yeast is carried out by the γ-glutamyl cycle as well as by the DUG complex. One of the last steps in the γ-glutamyl cycle is the cleavage of Cys-Gly by a peptidase to the constitutent amino acids. Saccharomyces cerevisiae extracts carry Cys-Gly dipeptidase activity, but the corresponding gene has not yet been identified. We describe the isolation and characterization of a novel Cys-Gly dipeptidase, encoded by the DUG1 gene. Dug1p had previously been identified as part of the Dug1p-Dug2p-Dug3p complex that operates as an alternate GSH degradation pathway and has also been suggested to function as a possible di- or tripeptidase based on genetic studies. We show here that Dug1p is a homodimer that can also function in a Dug2-Dug3-independent manner as a dipeptidase with high specificity for Cys-Gly and no activity toward tri- or tetrapeptides in vitro. This activity requires zinc or manganese ions. Yeast cells lacking Dug1p (dug1Δ) accumulate Cys-Gly. Unlike all other Cys-Gly peptidases, which are members of the metallopeptidase M17, M19, or M1 families, Dug1p is the first to belong to the M20A family. We also show that the Dug1p Schizosaccharomyces pombe orthologue functions as the exclusive Cys-Gly peptidase in this organism. The human orthologue CNDP2 also displays Cys-Gly peptidase activity, as seen by complementation of the dug1Δ mutant and by biochemical characterization, which revealed a high substrate specificity and affinity for Cys-Gly. The results indicate that the Dug1p family represents a novel class of Cys-Gly dipeptidases.GSH is a thiol-containing tripeptide (l-γ-glutamyl-l-cysteinyl-glycine) present in almost all eukaryotes (barring a few protozoa) and in a few prokaryotes (1). In the cell, glutathione exists in reduced (GSH) and oxidized (GSSG) forms. Its abundance (in the millimolar range), a relatively low redox potential (-240 mV), and a high stability conferred by the unusual peptidase-resistant γ-glutamyl bond are three of the properties endowing GSH with the attribute of an important cellular redox buffer. GSH also contributes to the scavenging of free radicals and peroxides, the chelation of heavy metals, such as cadmium, the detoxification of xenobiotics, the transport of amino acids, and the regulation of enzyme activities through glutathionylation and serves as a source of sulfur and nitrogen under starvation conditions (2, 3). GSH metabolism is carried out by the γ-glutamyl cycle, which coordinates its biosynthesis, transport, and degradation. The six-step cycle is schematically depicted in Fig. 1 (2).Open in a separate windowFIGURE 1.γ-Glutamyl cycle of glutathione metabolism. γ-Glutamylcysteine synthetase and GSH synthetase carry out the first two steps in glutathione biosynthesis. γ-glutamyltranspeptidase, γ-glutamylcyclotransferase, 5-oxoprolinase, and Cys-Gly dipeptidase are involved in glutathione catabolism. Activities responsible for γ-glutamylcyclotransferase and 5-oxoprolinase have not been detected in S. cerevisiae.In Saccharomyces cerevisiae, γ-glutamyl cyclotransferase and 5-oxoprolinase activities have not been detected, which has led to the suggestion of the presence of an incomplete, truncated form of the γ-glutamyl cycle (4) made of γ-glutamyl transpeptidase (γGT)⁴ and Cys-Gly dipeptidase and only serving a GSH catabolic function. Although γGT and Cys-Gly dipeptidase activities were detected in S. cerevisiae cell extracts, only the γGT gene (ECM38) has been identified so far. Cys-Gly dipeptidase activity has been identified in humans (5, 6), rats (7–10), pigs (11, 12), Escherichia coli (13, 14), and other organisms (15, 16), and most of them belong to the M17 or the M1 and M19 metallopeptidases gene families (17).S. cerevisiae has an alternative γGT-independent GSH degradation pathway (18) made of the Dug1p, Dug2p, and Dug3p proteins that function together as a complex. Dug1p also seem to carry nonspecific di- and tripeptidase activity, based on genetic studies (19).We show here that Dug1p is a highly specific Cys-Gly dipeptidase, as is its Schizosaccharomyces pombe homologue. We also show that the mammalian orthologue of DUG1, CNDP2, can complement the defective utilization of Cys-Gly as sulfur source of an S. cerevisiae strain lacking DUG1 (dug1Δ). Moreover, CNDP2 has Cys-Gly dipeptidase activity in vitro, with a strong preference for Cys-Gly over all other dipeptides tested. CNDP2 and its homologue CNDP1 are members of the metallopeptidases M20A family and have been known to carry carnosine (β-alanyl-histidine) and carnosine-like (homocarnosine and anserine) peptidase activity (20, 21). This study thus reveals that the metallopeptidase M20A family represents a novel Cys-Gly peptidase family, since only members of the M19, M1, and M17 family were known to carry this function.     

Maternal Smoking and the Risk of Cancer in Early Life – A Meta-Analysis

BackgroundIn spite of the well-known harmful effects on the fetus, many women continue smoking during pregnancy. Smoking as an important source of toxic chemicals may contribute to the developmental origin of diseases.ObjectivesThe aim of this work was to pursue the possible association between maternal smoking and cancer in early life. Specifically, we wanted to identify the associated early life cancer types, and to quantify the associations.MethodsIn a systematic literature search 825 articles were identified in PubMed and Web of Science, and 55 more through the reference lists. Of these 62 fulfilled the criteria for inclusion in meta-analyses. Using Mantel-Haenszel or DerSimonian and Laird method, depending on heterogeneity of the studies, pooled estimates and 95% confidence intervals for eight cancer types were calculated.ResultsSmoking during pregnancy was associated with an increased risk for for brain and central nervous system tumors (OR = 1.09; 95% CI = 1.02–1.17). Although the risk for lymphoma was also associated (OR = 1.21; 95% CI = 1.05–1.34), it did not hold up in subgroup analyses. Leukemia was not found to be associated with maternal smoking. Five other cancer types (bone, soft tissue, renal, hepatic, and germ cell cancer) were also examined, but the number of studies was too limited to exclude the possibility of maternal smoking as a risk factor for cancer in offspring.ConclusionsAccording to our meta-analyses, maternal smoking is associated with nervous system cancers, but not with leukemia in early life. Confirming or rejecting associations of maternal smoking with lymphoma and the five other cancer types requires further studies.     

Src Phosphorylation of ��-Receptor Is Responsible for the Receptor Switching from an Inhibitory to a Stimulatory Signal

Recent studies have revealed that in G protein-coupled receptor signalings switching between G protein- and β-arrestin (βArr)-dependent pathways occurs. In the case of opioid receptors, the signal is switched from the initial inhibition of adenylyl cyclase (AC) to an increase in AC activity (AC activation) during prolonged agonist treatment. The mechanism of such AC activation has been suggested to involve the switching of G proteins activated by the receptor, phosphorylation of signaling molecules, or receptor-dependent recruitment of cellular proteins. Using protein kinase inhibitors, dominant negative mutant studies and mouse embryonic fibroblast cells isolated from Src kinase knock-out mice, we demonstrated that μ-opioid receptor (OPRM1)-mediated AC activation requires direct association and activation of Src kinase by lipid raft-located OPRM1. Such Src activation was independent of βArr as indicated by the ability of OPRM1 to activate Src and AC after prolonged agonist treatment in mouse embryonic fibroblast cells lacking both βArr-1 and -2. Instead the switching of OPRM1 signals was dependent on the heterotrimeric G protein, specifically G_i2 α-subunit. Among the Src kinase substrates, OPRM1 was phosphorylated at Tyr³³⁶ within NPXXY motif by Src during AC activation. Mutation of this Tyr residue, together with mutation of Tyr¹⁶⁶ within the DRY motif to Phe, resulted in the complete blunting of AC activation. Thus, the recruitment and activation of Src kinase by OPRM1 during chronic agonist treatment, which eventually results in the receptor tyrosine phosphorylation, is the key for switching the opioid receptor signals from its initial AC inhibition to subsequent AC activation.Classical G protein-coupled receptor (GPCR)² signaling involves the activation of specific heterotrimeric G proteins and the subsequent dissociation of α- and βγ-subunits. These G protein subunits serve as the activators and/or inhibitors of several effector systems, including adenylyl cyclases, phospholipases, and ion channels (1). However, recent studies have shown that GPCR signaling deviates from such a classical linear model. For example, in kidney and colonic epithelial cells, protease-activated receptor 1 can transduce its signals through either Gα_i/o or Gα_q subunits via inhibition of small GTPase RhoA or activation of RhoD. Thus, RhoA and RhoD act as molecular switches between the negative and positive signaling activity of protease-activated receptor 1 (2). Another example is the ability of β₂-adrenergic receptor to switch from G_s-dependent pathways to non-classical signaling pathways by coupling to pertussis toxin-sensitive G_i proteins in a cAMP-dependent protein kinase/protein kinase C phosphorylation-dependent manner. In this case, the phosphorylation-induced switch in G protein coupling provides the receptor access to alternative signaling pathways. For β₂-adrenergic receptors, this leads to a G_i-dependent activation of MAP kinase (3, 4). Furthermore the involvement of protein scaffolds, such as β-arrestins in the MAP kinase cascade, could also alter the GPCR signaling (5–8). Hence the formation of “signaling units” or “receptosomes” would influence the GPCR signaling process and destination.For opioid receptors, which are members of the rhodopsin GPCR subfamily receptors, signal switching is also observed. Normally opioid receptors inhibit AC activity, activate the MAP kinases and Kir3 K⁺ channels, inhibit the voltage-dependent Ca²⁺ channels, and regulate other effectors such as phospholipase C (9). However, during prolonged agonist treatment, not only is there a blunting of these cellular responses but also a compensatory increase in intracellular cAMP level, which is particularly significant upon the removal of the agonist or the addition of an antagonist such as naloxone (10–12). This compensatory adenylyl cyclase activation phenomenon has been postulated to be responsible for the development of drug tolerance and dependence (13). The observed change from receptor-mediated AC inhibition to receptor-mediated AC activation reflects possible receptor signal switching. Although the exact mechanism for such signal changes has yet to be elucidated, activation of specific protein kinases and subsequent phosphorylation of AC isoforms (14, 15) and other signaling molecules (16) have been suggested to be the key for observed AC activation. Among all the protein kinases studied, involvement of protein kinase C, MAP kinase, and Raf-1 has been implicated in the activation of AC (17–19). Alternative mechanisms, such as agonist-induced receptor internalization and the increase in the constitutive activities of the receptor, also have been suggested to play a role in increased AC activity after prolonged opioid agonist treatment (20). Earlier studies also implicated the switching of the opioid receptor from G_i/G_o to G_s coupling during chronic agonist treatment (21). Regardless of the mechanism, the exact molecular events that lead to the switching of opioid receptor from an inhibitory response to a stimulatory response remain elusive.Src kinases, which are members of the nonreceptor tyrosine kinase family, have been implicated in GPCR function because several Src family members such as cSrc, Fyn, and Yes have been reported to be activated by several GPCRs, including β₂- (22) and β₃ (23)-adrenergic, M₂- (24) and M₃ (25)-muscarinic, and bradykinin receptors (26). The GPCRs that are capable of activating Src predominantly couple to G_i/o family G proteins (27). Src kinases appear to associate with, and be activated by, GPCRs themselves either through direct interaction with intracellular receptor domains or by binding to GPCR-associated proteins, such as G protein subunits or β-arrestins (27). Src kinase has been reported to be activated by κ- (28) and δ (29)-opioid receptors and regulate the c-Jun kinase and MAP kinase activities. Src kinase within the nucleus accumbens has been implicated in the rewarding effect and hyperlocomotion induced by morphine in mice (30). However, it is not clear whether the Src kinase is activated and involved in the signal transduction in AC activation after chronic opioid agonist administration.Previously we reported that the lipid raft location of the receptor and the Gα_i2 proteins are two prerequisites for the observed increase in AC activity during prolonged agonist treatment (31, 32). Because various protein kinases including Src kinases and G proteins have been shown to be enriched in lipid rafts (33), the roles of these cellular proteins in the eventual switching of opioid receptor signals from inhibition to stimulation of AC activity were examined in the current studies. We were able to demonstrate that the association with and subsequent activation of Src kinase by the μ-opioid receptor (OPRM1), which leads to eventual tyrosine phosphorylation of OPRM1, are the cellular events required for the switching of opioid receptor signaling upon chronic agonist treatment.     

“The Instinct Concept of the Early Konrad Lorenz”

Peculiar to Konrad Lorenz’s view of instinctive behavior is his strong innate-learned dichotomy. He claimed that there are neither ontogenetic nor phylogenetic transitions between instinctive and experience-based behavior components, thus contradicting all former accounts of instinct. The present study discusses how Lorenz came to hold this controversial position by examining the history of Lorenz’s early theoretical development in the crucial period from 1931 to 1937, taking relevant influences into account. Lorenz’s intellectual development is viewed as being guided by four theoretical and practical commitments as to how to study and explain behavior. These four factors, which were part of the general approach of Lorenz but not of other animal psychologists, were crucial in bringing about his specific position on instinctive behavior.     

Numerical Approaches to Life Cycle Interpretation - The case of the Ecoinvent’96 database (10 pp)

Goal, Scope and Background To strengthen the evaluative power of LCA, life cycle interpretation should be further developed. A previous contribution (Heijungs & Kleijn 2001) elaborated five examples of concrete methods within the subset of numerical approaches towards interpretation. These methods were: contribution analysis, perturbation analysis, uncertainty analysis, comparative analysis, and discernibility analysis. Developments in software have enabled the possibility to apply the five example methods to explore the much-used Ecoinvent”96 database.Discussion of Methods The numerical approaches implemented in this study include contribution analysis, perturbation analysis, uncertainty analysis, comparative analysis, discernibility analysis and the newly developed key issue analysis. The data used comes from a very large process database: Ecoinvent’96, containing 1163 processes, 1181 economic flows and 571 environmental flows. Conclusions Results are twofold: they serve as a benchmark to the usefulness and feasibility of these numerical approaches, and they shed light on the question of stability and structure in an often-used large system of interconnected processes. Most of the approaches perform quite well: computation time on a moderate PC is between a few seconds a few minutes. Only Monte Carlo analyses may require much longer, but even then it appears that most questions can be answered within a few hours. Moreover, analytical expressions for error propagation are much faster than Monte Carlo analyses, while giving almost identical results. Despite the fact that many processes are connected to each other, leading to the possibility of a very unstable system and very sensitive coefficients, the overall results show that most results are not extremely uncertain. There are, however, some exceptions to this positive message.     

The Bactericidal Activity of Carbon Monoxide–Releasing Molecules against Helicobacter pylori

Helicobacter pylori is a pathogen that establishes long life infections responsible for chronic gastric ulcer diseases and a proved risk factor for gastric carcinoma. The therapeutic properties of carbon-monoxide releasing molecules (CORMs) led us to investigate their effect on H. pylori. We show that H. pylori 26695 is susceptible to two widely used CORMs, namely CORM-2 and CORM-3. Also, several H. pylori clinical isolates were killed by CORM-2, including those resistant to metronidazole. Moreover, sub-lethal doses of CORM-2 combined with metronidazole, amoxicillin and clarithromycin was found to potentiate the effect of the antibiotics. We further demonstrate that the mechanisms underpinning the antimicrobial effect of CORMs involve the inhibition of H. pylori respiration and urease activity. In vivo studies done in key cells of the innate immune system, such as macrophages, showed that CORM-2, either alone or when combined with metronidazole, strongly reduces the ability of H. pylori to infect animal cells. Hence, CORMs have the potential to kill antibiotic resistant strains of H. pylori.     

Life is a huge compromise: Is the complexity of the vertebrate immune-neuroendocrine system an advantage or the price to pay?

Recent advances in comparative immunology have established that invertebrates produce hypervariable molecules probably related to immunity, suggesting the possibility of raising a specific immune response. “Priming” and “tailoring” are terms now often associated with the invertebrate innate immunity. Comparative immunologists contributed to eliminate the idea of a static immune system in invertebrates, making necessary to re-consider the evolutive meaning of immunological memory of vertebrates. If the anticipatory immune system represents a maximally efficient immune system, why can it be observed only in vertebrates, especially in consideration that molecular hypervariability exists also in invertebrates? Using well-established theories concerning the evolution of the vertebrate immunity as theoretical basis we analyze from an Eco-immunology-based perspective why a memory-based immune system may have represented an evolutive advantage for jawed vertebrates. We hypothesize that for cold-blooded vertebrates memory represents a complimentary component that flanks the robust and fundamental innate immunity. Conversely, immunological memory has become indispensable and fully exploited in warm-blooded vertebrates, due to their stable inner environment and high metabolic rate, respectively.     

The Role of the ��DELSEED-loop of ATP Synthase

ATP synthase uses a unique rotational mechanism to convert chemical energy into mechanical energy and back into chemical energy. The helix-turn-helix motif, termed “DELSEED-loop,” in the C-terminal domain of the β subunit was suggested to be involved in coupling between catalysis and rotation. Here, the role of the DELSEED-loop was investigated by functional analysis of mutants of Bacillus PS3 ATP synthase that had 3–7 amino acids within the loop deleted. All mutants were able to catalyze ATP hydrolysis, some at rates several times higher than the wild-type enzyme. In most cases ATP hydrolysis in membrane vesicles generated a transmembrane proton gradient, indicating that hydrolysis occurred via the normal rotational mechanism. Except for two mutants that showed low activity and low abundance in the membrane preparations, the deletion mutants were able to catalyze ATP synthesis. In general, the mutants seemed less well coupled than the wild-type enzyme, to a varying degree. Arrhenius analysis demonstrated that in the mutants fewer bonds had to be rearranged during the rate-limiting catalytic step; the extent of this effect was dependent on the size of the deletion. The results support the idea of a significant involvement of the DELSEED-loop in mechanochemical coupling in ATP synthase. In addition, for two deletion mutants it was possible to prepare an α₃β₃γ subcomplex and measure nucleotide binding to the catalytic sites. Interestingly, both mutants showed a severely reduced affinity for MgATP at the high affinity site.F₁F₀-ATP synthase catalyzes the final step of oxidative phosphorylation and photophosphorylation, the synthesis of ATP from ADP and inorganic phosphate. F₁F₀-ATP synthase consists of the membrane-embedded F₀ subcomplex, with, in most bacteria, a subunit composition of ab₂c₁₀, and the peripheral F₁ subcomplex, with a subunit composition of α₃β₃γδε. The energy necessary for ATP synthesis is derived from an electrochemical transmembrane proton (or, in some organisms, a sodium ion) gradient. Proton flow down the gradient through F₀ is coupled to ATP synthesis on F₁ by a unique rotary mechanism. The protons flow through (half) channels at the interface of the a and c subunits, which drives rotation of the ring of c subunits. The c₁₀ ring, together with F₁ subunits γ and ε, forms the rotor. Rotation of γ leads to conformational changes in the catalytic nucleotide binding sites on the β subunits, where ADP and P_i are bound. The conformational changes result in the formation and release of ATP. Thus, ATP synthase converts electrochemical energy, the proton gradient, into mechanical energy in the form of subunit rotation and back into chemical energy as ATP. In bacteria, under certain physiological conditions, the process runs in reverse. ATP is hydrolyzed to generate a transmembrane proton gradient, which the bacterium requires for such functions as nutrient import and locomotion (for reviews, see Refs. 1–6).F₁ (or F₁-ATPase) has three catalytic nucleotide binding sites located on the β subunits at the interface to the adjacent α subunit. The catalytic sites have pronounced differences in their nucleotide binding affinity. During rotational catalysis, the sites switch their affinities in a synchronized manner; the position of γ determines which catalytic site is the high affinity site (K_d1 in the nanomolar range), which site is the medium affinity site (K_d2 ≈ 1 μm), and which site is the low affinity site (K_d3 ≈ 30–100 μm; see Refs. 7 and 8). In the original crystal structure of bovine mitochondrial F₁ (9), one of the three catalytic sites, was filled with the ATP analog AMP-PNP,² a second was filled with ADP (plus azide) (see Ref. 10), and the third site was empty. Hence, the β subunits are referred to as β_TP, β_DP, and β_E. The occupied β subunits, β_TP and β_DP, were in a closed conformation, and the empty β_E subunit was in an open conformation. The main difference between these two conformations is found in the C-terminal domain. Here, the “DELSEED-loop,” a helix-turn-helix structure containing the conserved DELSEED motif, is in an “up” position when the catalytic site on the respective β subunit is filled with nucleotide and in a “down” position when the site is empty (Fig. 1A). When all three catalytic sites are occupied by nucleotide, the previously open β_E subunit assumes an intermediate, half-closed (β_HC) conformation. It cannot close completely because of steric clashes with γ (11).Open in a separate windowFIGURE 1.The βDELSEED-loop. A, interaction of the β_TP and β_E subunits with theγ subunit.β subunits are shown in yellow andγ in blue. The DELSEED-loop (shown in orange, with the DELSEED motif itself in green)of β_TP interacts with the C-terminal helixγ and the short helix that runs nearly perpendicular to the rotation axis. The DELSEED-loop of β_E makes contact with the convex portion of γ, formed mainly by the N-terminal helix. A nucleotide molecule (shown in stick representation) occupies the catalytic site of β_TP, and the subunit is in the closed conformation. The catalytic site on β_E is empty, and the subunit is in the open conformation. This figure is based on Protein Data Bank file 1e79 (32). B, deletions in the βDELSEED-loop. The loop was “mutated” in silico to represent the PS3 ATP synthase. The 3–4-residue segments that are removed in the deletion mutants are color-coded as follows: ³⁸⁰LQDI³⁸³, pink; ³⁸⁴IAIL³⁸⁷, green; ³⁸⁸GMDE³⁹¹, yellow; ³⁹²LSD³⁹⁴, cyan; ³⁹⁵EDKL³⁹⁸, orange; ³⁹⁹VVHR⁴⁰², blue. Residues that are the most involved in contacts with γ are labeled. All figures were generated using the program PyMOL (DeLano Scientific, San Carlos, CA).The DELSEED-loop of each of the three β subunits makes contact with the γ subunit. In some cases, these contacts consist of hydrogen bonds or salt bridges between the negatively charged residues of the DELSEED motif and positively charged residues on γ. The interactions of the DELSEED-loop with γ, its movement during catalysis, the conservation of the DELSEED motif (see 12–14). Thus, the finding that an AALSAAA mutant in the α₃β₃γ complex of ATP synthase from the thermophilic Bacillus PS3, where several hydrogen bonds/salt bridges to γ are removed simultaneously, could drive rotation of γ with the same torque as the wild-type enzyme (14) came as a surprise. On the other hand, it seems possible that it is the bulk of the DELSEED-loop, more so than individual interactions, that drives rotation of γ. According to a model favored by several authors (6, 15, 16) (see also Refs. 17–19), binding of ATP (or, more precisely, MgATP) to the low affinity catalytic site on β_E and the subsequent closure of this site, accompanied by its conversion into the high affinity site, are responsible for driving the large (80–90°) rotation substep during ATP hydrolysis, with the DELSEED-loop acting as a “pushrod.” A recent molecular dynamics (20) study supports this model and implicates mainly the region around several hydrophobic residues upstream of the DELSEED motif (specifically βI386 and βL387)³ as being responsible for making contact with γ during the large rotation substep.

TABLE 1

Conservation of residues in the DELSEED-loop Amino acids found in selected species in the turn region of the DELSEED-loop. Listed are all positions subjected to deletions in the present study. Residue numbers refer to the PS3 enzyme. Consensus annotation: p, polar residue; s, small residue; h, hydrophobic residue; –, negatively charged residue; +, positively charged residue.Open in a separate windowIn the present study, we investigated the function of the DELSEED-loop using an approach less focused on individual residues, by deleting stretches of 3–7 amino acids between positions β380 and β402 of ATP synthase from the thermophilic Bacillus PS3. We analyzed the functional properties of the deletion mutants after expression in Escherichia coli. The mutants showed ATPase activities, which were in some cases surprisingly high, severalfold higher than the activity of the wild-type control. On the other hand, in all cases where ATP synthesis could be measured, the rates where below or equal to those of the wild-type enzyme. In Arrhenius plots, the hydrolysis rates of the mutants were less temperature-dependent than those of wild-type ATP synthase. In those cases where nucleotide binding to the catalytic sites could be tested, the deletion mutants had a much reduced affinity for MgATP at high affinity site 1. The functional role of the DELSEED-loop will be discussed in light of the new information.     

The date palm—“Tree of Life”in the subtropical deserts

Dates, staple food in the valleys of the Tigris, Euphrates and Nile rivers since the dawn of history, have been established on nearly 6,000 acres in southern California and Arizona.     

Revisiting the “Cdk-Centric” View of the Mammalian Cell Cycle

Since the early genetic studies in yeast, regulation of the cell cycle has been associated to the sequential activation of several proline-directed serine-threonine protein kinases by cyclins. From yeast to humans, the activiy of these cyclin-dependent kinases (Cdks) have been thought to be essential for cell cycle regulation. Recent gene-targeted mouse models for different cyclins and Cdks have shown that members of these families show a certain level of redundancy and that specific complexes are not required for the mitotic cell cycle. However, the complexity of the Cdk-cyclin network and the promiscuity of their members makes it difficult to understand the relative contribution of these proteins to the mammalian cell division cycle. Compensatory roles by non-Cdk activities and Cdk-independent functions of cyclins are increasing the complexity of the current simplistic models. We still do not know whether at least one cyclin-dependent kinase activity is required for cell cycle progression in mammalian cells. Indeed, a relevant question for cancer therapy.