Type I chaperonins: not all are created equal

Type I chaperonins play an essential role in the folding of newly translated and stress-denatured proteins in eubacteria, mitochondria and chloroplasts. Since their discovery, the bacterial chaperonins have provided an excellent model system for investigating the mechanism by which chaperonins mediate protein folding. Due to the high conservation of the primary sequence among Type I chaperonins, it is generally accepted that organellar chaperonins function similar to the bacterial ones. However, recent studies indicate that the chloroplast and mitochondrial chaperonins possess unique structural and functional properties that distinguish them from their bacterial homologs. This review focuses on the unique properties of organellar chaperonins.     

Targeting mechanisms in myelinated axons: not all nodes are created equal

A recent Neuron paper by Zhang et al. (2012) reveals how ion channels and adhesion molecules essential for rapid nerve conduction in vertebrates are differentially targeted to nodes of Ranvier. Moreover, distinct mechanisms regulate initial clustering and maintenance of specific nodal components.     

Novel object exploration in mice: not all objects are created equal

Object exploration is an increasingly popular experimental paradigm in behavioral sciences. We have begun a series of studies with mice specifically looking at the parameters that influence behaviors in this test. The aim of the present study was to examine the effect of object type on performance in the object exploration test. More specifically, adult male C57BL/6J mice were trained and tested using objects that could be climbed (CLIMB) or with those that could only be touched (TOUCH). The results show that activity is affected by the presentation of objects, with object type interacting with some of these changes. C57 mice explored objects that can be climbed over significantly longer than objects that can only be touched and a more rapid habituation was observed using objects that could only be touched. Robust recognition memory was observed in both groups of mice, however mice in the CLIMB group exhibited a significantly greater discrimination index compared to mice in the TOUCH group. Taken together, these findings demonstrate that the selection of objects is of critical importance and it is recommended that special attention be given to the functional (affordant) properties of the objects to-be-used in future studies.     

The genome of Brugia malayi - all worms are not created equal

Filarial nematode parasites, the causative agents of elephantiasis and river blindness, undermine the livelihoods of over one hundred million people in the developing world. Recently, the Filarial Genome Project reported the draft sequence of the ~95 Mb genome of the human filarial parasite Brugia malayi - the first parasitic nematode genome to be sequenced. Comparative genome analysis with the prevailing model nematode Caenorhabditis elegans revealed similarities and differences in genome structure and organization that will prove useful as additional nematode genomes are completed. The Brugia genome provides the first opportunity to comprehensively compare the full gene repertoire of a free-living nematode species and one that has evolved as a human pathogen. The Brugia genome also provides an opportunity to gain insight into genetic basis for mutualism, as Brugia, like a majority of filarial species, harbors an endosybiotic bacterium (Wolbachia). The goal of this review is to provide an overview of the results of genomic analysis and how these observations provide new insights into the biology of filarial species.     

All progestins are not created equal

A variety of progestins are available for therapeutic use. It is convenient to classify them into those related in chemical structure to progesterone or testosterone. Progestins related to progesterone can be subdivided into pregnanes and 19-norpregnanes, whereas those related to testosterone can be subdivided into those with and without a 17-ethinyl group. 17-Ethinylated progestins consist of the families of norethindrone (estranes) and levonorgestrel (13-ethylgonanes). Progestins administered orally undergo extensive hepatic first pass metabolism primarily by reduction and conjugation, and in most instances, relatively high progestin doses are required for therapeutic use. There are limited reliable data on the pharmacokinetics of most progestins. Some progestins are prodrugs, requiring transformation prior to exhibiting progestational activity. Qualitative and quantitative tests utilizing either human or animal species have been used to establish progestin potency. However, profound differences in progestational activity are often observed between human and animal tissues. Also, there is a misconception about androgenicity of progestins due largely to extrapolation of data from rat studies to the human. Progestins differ widely in their chemical structures, structure-function relationships, metabolism, pharmacokinetics, and potencies; they are not created equal.     

Ty1 proteolytic cleavage sites are required for transposition: all sites are not created equal

The retroviral protease is a key enzyme in a viral multienzyme complex that initiates an ordered sequence of events leading to virus assembly and propagation. Viral peptides are initially synthesized as polyprotein precursors; these precursors undergo a number of proteolytic cleavages executed by the protease in a specific and presumably ordered manner. To determine the role of individual protease cleavage sites in Ty1, a retrotransposon from Saccharomyces cerevisiae, the cleavage sites were systematically mutagenized. Altering the cleavage sites of the yeast Ty1 retrotransposon produces mutants with distinct retrotransposition phenotypes. Blocking the Gag/PR site also blocks cleavage at the other two cleavage sites, PR/IN and IN/RT. In contrast, mutational block of the PR/IN or IN/RT sites does not prevent cleavage at the other two sites. Retrotransposons with mutations in each of these sites have transposition defects. Mutations in the PR/IN and IN/RT sites, but not in the Gag/PR site, can be complemented in trans by endogenous Ty1 copies. Hence, the digestion of the Gag/PR site and release of the protease N terminus is a prerequisite for processing at the remaining sites; cleavage of PR/IN is not required for the cleavage of IN/RT, and vice versa. Of the three cleavage sites in the Gag-Pol precursor, the Gag/PR site is processed first. Thus, Ty1 Gag-Pol processing proceeds by an ordered pathway.     

All KLH preparations are not created equal

Keyhole limpet hemocyanin (KLH) preparations used for dermal testing in human volunteers may contain factors which elicit false positive reactions. These factors can be associated with the hemolymph collection procedure and possibly to a change in collection beds by the limpet supplier. Rapid collection of hemolymph from animals obtained from specified limpet beds resulted in KLH which produced negligible dermal reactivity in normal individuals.     

Telomeres: not all breaks are equal

ATM, Rad50 and Mre11 have been shown to prevent telomere fusion in Drosophila, thereby extending the protective role of DNA damage checkpoint proteins to non-canonical telomeres formed without telomerase. How do these proteins help chromosomal termini escape fusion through 'repair' while promoting repair of induced DNA breaks?     

According to the CPLL proteome sheriffs,not all aperitifs are created equal!

Combinatorial peptide ligand libraries (CPLLs) have been adopted for investigating the proteome of a popular aperitif in Northern Italy, called “Amaro Branzi”, stated to be an infusion of a secret herbal mixture, of which some ingredients are declared on the label, namely Angelica officinalis, Gentiana lutea and orange peel, sweetened by a final addition of honey. In order to assess the genuineness of this commercial liqueur, we have prepared extracts of the three vegetable ingredients, assessed their proteomes, and compared them to the one found in the aperitif. The amaro's proteome was identified via prior capture with CPLLs at two different pH values (2.2 and 4.8). Via mass spectrometry analysis of the recovered fractions, after elution of the captured populations in 4% boiling SDS, we could confirm the presence of the following: six proteins originating from honey, 11 from orange peels, 29 from G. lutea and 46 from A. officinalis (including shared species), plus 33 species which could not be attributed to the other secret ingredients, due to paucity of genomic data on plant proteins, for a total of 93 unique gene products (merging shared proteins). This fully confirmed the genuineness of the product. Considering that most of these species could be present in trace amounts, undetectable by conventional techniques, the CPLL methodology, due to its ability to enhance the signal of trace components up to 3 to 4 orders of magnitude, could represent a powerful tool for investigating the genuineness and natural origin of commercial beverages in order to protect consumers from adulterated products.     

DNA double strand breaks: Not all foci are created equal

Comment on: Processing of O6-methylguanine into DNA double-strand breaks requires two rounds of replication whereas apoptosis is also induced in subsequent cell cycles. Quiros S, et al. Cell Cycle 2010; 9:In press.     

Actin nucleation: Nucleation-promoting factors are not all equal

Arp2/3 complex plays a key role in regulated actin polymerization. A recent study has revealed marked differences in the ability of two nucleation-promoting factors - N-WASP and Scar/WAVE1 - to activate the Arp2/3 complex. Further insights have come from determination of the Arp2/3 crystal structure.     

Not all secretory granules are created equal: Partitioning of soluble content proteins

Secretory granules carrying fluorescent cargo proteins are widely used to study granule biogenesis, maturation, and regulated exocytosis. We fused the soluble secretory protein peptidylglycine alpha-hydroxylating monooxygenase (PHM) to green fluorescent protein (GFP) to study granule formation. When expressed in AtT-20 or GH3 cells, the PHM-GFP fusion protein partitioned from endogenous hormone (adrenocorticotropic hormone, growth hormone) into separate secretory granule pools. Both exogenous and endogenous granule proteins were stored and released in response to secretagogue. Importantly, we found that segregation of content proteins is not an artifact of overexpression nor peculiar to GFP-tagged proteins. Neither luminal acidification nor cholesterol-rich membrane microdomains play essential roles in soluble content protein segregation. Our data suggest that intrinsic biophysical properties of cargo proteins govern their differential sorting, with segregation occurring during the process of granule maturation. Proteins that can self-aggregate are likely to partition into separate granules, which can accommodate only a few thousand copies of any content protein; proteins that lack tertiary structure are more likely to distribute homogeneously into secretory granules. Therefore, a simple "self-aggregation default" theory may explain the little acknowledged, but commonly observed, tendency for both naturally occurring and exogenous content proteins to segregate from each other into distinct secretory granules.