Can photosynthesis provide a `biological blueprint'' for the design of novel solar cells?

The primary photochemical reactions in purple-bacterial photosynthesis take place in discrete, membrane-bound pigment–protein complexes called reaction centres and light-harvesting complexes. The detailed information on their structure and function now available is being used to aid the design and construction of novel solar-energy converters.     

Effects of desiccation on photosynthesis pigments and the ELIP-like dsp 22 protein complexes in the resurrection plant Craterostigma plantagineum

Desiccation and abscisic acid treatment lead to major changes in thylakoid membranes of the desiccation-tolerant plant Craterostigma plantagineum. The chlorophyll contents and proteins of the light harvesting complexes decrease during desiccation, although some chlorophyll is retained in the dehydrated state. The xanthophyll cycle pigment zeaxanthin, however, increased. Under these conditions, a 22 kDa ELIP-like desiccation-induced protein (dsp 22) accumulated in the thylakoid membranes. Fractionation of pigment–protein complexes of stressed plants revealed that the dsp 22 protein co-localized with the carotenoid zeaxanthin. Inhibition of zeaxanthin production had a negative effect on the accumulation of the dsp 22 protein. It is suggested that dsp 22 contributes to the protection against photoinhibition caused by dehydration.     

A neutral polypeptide—calcium ion complex

Proton magnetic resonance studies have been utilized to demonstrate calcium binding to a neutral polypeptide containing only peptide functional groups, i.e. cyclo-(—Gly—Gly—Val—Pro—)₃. This provides an explicit basis for the previously proposed neutral site theory for the binding of Ca²⁺ to polypeptides and protein wherein the peptide oxygens directly coordinate the Ca²⁺.     

High-performance liquid chromatography and studies of neurophysin—neurohypophysial hormone pathways

High-performance liquid chromatography (HPLC) is being used extensively to characterize active polypeptides, precursor processing mechanisms, and cooperative peptide—protein noncovalent complexes in neuroendocrine pathways for neurohypophysial peptide hormones, oxytocin and vasopressin, and the hormone-associated proteins, neurophysins. Reversed-phase and ion-exchange HPLC polypeptide mapping have been used to detect the hormones, associated proteins, and other molecular forms containing these. This mapping but also ultimately to identify anatomical sites which contain the neurophysin/ hormone molecular pathways and to define the relatedness of polypeptide forms contained in different pathways. Reversed-phase HPLC also has provided a means to study proteolytic precursor processing, both to isolate synthetic and semisynthetic polypeptides and intermediates produced by these reactions. Finally, bioaffinity HPLC is being evaluated as a separatory and analytical tool. The latter includes its use to characterize the noncovalent peptide—protein and protein—protein interactions which occur among the molecular forms of the neurophysin/hormone pathways. These experiments typify the impact of HPLC for both analytical and preparative separations in studies of biologically active peptides and proteins.     

Localization of two homologous Arabidopsis kinesin-related proteins in the phragmoplast

During plant cytokinesis, kinesin-related motor proteins are believed to play critical roles in microtubule organization and vesicle transport in the phragmoplast. Previously, we reported that the motor AtPAKRP1 was associated with the plus end of phragmoplast microtubules in Arabidopsis thaliana [Lee Y-RJ, Liu B (2000) Curr Biol 10:797–800]. In this paper, we report a full-length cDNA from the same organism, which encodes a polypeptide 74% identical to AtPAKRP1. This AtPAKRP1-like protein—AtPAKRP1L—and AtPAKRP1 share similar domain structures along the polypeptides. Peptide antibodies were raised and purified to distinguish the two polypeptides in vitro and in vivo. When monospecific anti-AtPAKRP1 and anti-AtPAKRP1L antibodies were used in immunofluorescence, they both decorated the plus end of phragmoplast microtubules at all stages of phragmoplast development. Their localization patterns were indistinguishable from each other. By using bacterially expressed fusion proteins of motor-less versions of both polypeptides, it was revealed that AtPAKRP1 and AtPAKRP1L were able to interact with themselves and with each other. Using T-DNA insertional mutants, it was also demonstrated that AtPAKRP1 and AtPAKRP1L were not required for each others localization. Our results therefore indicate that AtPAKRP1 and AtPAKRP1L are both expressed in the same cells, and likely have identical functions in the phragmoplast by forming either homodimers or heterodimers.Abbreviations AtPAKRP1 Arabidopsis thaliana phragmoplast-associated kinesin-related protein 1 - AtPAKRP1L A. thaliana phragmoplast-associated kinesin-related protein 1-like - GST Glutathione S-transferase - KRP Kinesin-related protein - 6×His Six-histidine tag     

Photosystem II-based biosensors for the detection of pollutants

Photosystem II (PSII) is the supramolecular pigment–protein complex in the chloroplast, which catalyses the light-induced transfer of electrons from water to plastoquinone (PQ) in a process that evolves oxygen. The PSII complex is also known to bind some groups of (photosynthetic) herbicides, heavy metals and other chemical substances that affect its activity. The objective of this study is to provide an overview of the systems available for the bioassay of pollutants using biosensors that are based on the photochemical activity of PSII. Some applications of the PSII-based biosensors including herbicide, heavy metal monitoring and the detection of radiation in space experiments are reported.     

Polypeptide Compositions and NH2-terminal Amino Acid Sequences of Proteins in Foxtail and Proso Millets

Seed protein of foxtail and proso millets were fractionated into polypeptides that were analyzed for their major protein, prolamin, and the NH₂-terminal amino acid sequences of the proteins were determined. The proteins extracted from foxtail and proso millets were 64.1% and 80.0% prolamin, respectively. The polypeptides of the prolamins were classified into two groups. The major polypeptides of 27-19 kDa were rich in leucine and alanine, whereas the 17-14 kDa polypeptides were rich in methionine and cysteine. Glutelin-like proteins that were extracted with a reducing reagent were high in proline content, the major polypeptides being 17 and 20 kDa. The NH₂-terminal amino acid sequence showed that the major polypeptides of prolamin were homologous to α-zein and a glutelin-like protein containing the Pro-Pro-Pro sequence, like the repetitive sequence of γ-zein. Although the prolamin consisted of a similar subunit to that of zein, polypeptides with various pI values were found among them.     

Uptake and incorporation of the products of proteolysis by the rumen bacteriumBacteroides ruminicola R8/4

The polypeptides of the proteolytic rumen bacteriumBacteroides ruminicola R8/4 grown in the presence of either leaf Fraction 1 protein, bovine serum albumin, or Bactocasitone as sole nitrogen source were separated by SDS-polyacrylamide gel electrophoresis. Over 40 polypeptides were resolved; the pattern for organisms grown on Fraction 1 protein was similar but not identical to that of the serum albumin and Bactocasitone-grown bacteria. All the bacterial polypeptides were distinguishable from the polypeptides of Fraction 1 protein (and serum albumin). The stained pattern was the same for organisms sampled at intervals during the growth of a batch culture. After incubation of the growing organisms with [¹⁴C]-Fraction 1 protein, all the bacterial polypeptides were labeled. Bacteria grown in the presence of nonlabeled Fraction 1 protein and a mixture of [^14C]-labeled amino acids incorporated label into all the polypeptides; the bacteria did not grow in the absence of intact protein, and then virtually no label was incorporated from the amino acid mixture.     

Calpain II induced insolubilization of lens β-crystallin polypeptides may induce cataract

Addition of calpain II (EC 3.4.22.17) to soluble proteins from 10-day-old rat lens caused an increase in turbidity and production of water-insoluble protein. The insolubilization increased with higher concentrations of both lens protein and calpain II, it could be prevented by the cysteine protease inhibitor E-64; it required at least 0.5 mM Ca²⁺, it was limited to 6% of the soluble protein present and resulted from precipitation β-crystallin polypeptides. When compared by two-dimensional electrophoresis, the insoluble β-crystallin polypeptides produced by calpain II were similar to insoluble β-crystallin polypeptides found incataractous lenses. Trypsin also caused insolubilization of β-crystallin polypeptides, but these polypeptides were unlike polypeptides produced during cataract formation. These data suggested that the loss of solubility was due to a specific removal of N/or C-terminal extensions from β-crystallin polypeptides by calpain II, and that a similar process may occur in vivo during cataract formation. It is hypothesized that the insoluble protein produced by calpain II causes cataract by increasing light scatter in the lens.     

Indentification of β-oxidation enzymes among peroxisomal polypeptides: Increase in Coomassie blue-stainable protein after clofibrate treatment

Peroxisomes contain enzymes catalyzing the β-oxidation of fatty acids, which have been purified and partially characterized. Hypolipidemic drugs, including clofibrate, cause a marked proliferation of peroxisomes and a striking increase in the activity of their β-oxidation system. We have compared by sodium dodecyl sulfate—polyacrylamide gel electrophoresis the polypeptide patterns of normal and clofibrate-induced peroxisomes and the purified β-oxidation enzymes. The data allow a tentative identification of the β-oxidation enzymes among the peroxisomal polypeptides; these enzymes constitute only a small part of the protein of normal peroxisomes. A subset of peroxisomal polypeptides, including the β-oxidation enzymes, is preferentially increased by clofibrate.     

Bovine seminal ribonuclease: Non-hyperbolic kinetics in the second reaction step

Peroxisomes contain enzymes catalyzing the β-oxidation of fatty acids, which have been purified and partially characterized. Hypolipidemic drugs, including clofibrate, cause a marked proliferation of peroxisomes and a striking increase in the activity of their β-oxidation system. We have compared by sodium dodecyl sulfate—polyacrylamide gel electrophoresis the polypeptide patterns of normal and clofibrate-induced peroxisomes and the purified β-oxidation enzymes. The data allow a tentative identification of the β-oxidation enzymes among the peroxisomal polypeptides; these enzymes constitute only a small part of the protein of normal peroxisomes. A subset of peroxisomal polypeptides, including the β-oxidation enzymes, is preferentially increased by clofibrate.     

Two-dimensional gel electrophoretic analysis of Escherichia coli proteins: influence of various anaerobic growth conditions and the fnr gene product on cellular protein composition

Two-dimensional gel electrophoresis was used to examine the response of the cellular proteins of Escherichia coli to various anaerobic growth conditions and to the presence or absence of a functional Fnr protein. The steady-state levels of 125 polypeptides were found to vary in either a positive or negative manner, with many polypeptides being affected under a number of conditions. A large number (21) of the anaerobically inducible polypeptides were shown to be totally independent of the presence of Fnr while 22 were shown to be reduced in a fnr mutant under all anaerobic growth conditions tested. A total of 8 proteins were shown to be reduced in a fnr mutant only in aerobically grown cells indicating that the Fnr protein has a function in the presence of oxygen. This was further confirmed by the observation that 15 anaerobically inducible polypeptides were also found to show an increase in aerobically grown cells, however, only in a fnr strain. This latter finding implies that Fnr may also exhibit repressor function. This effect of Fnr-dependent repression was also observed with several polypeptides in anaerobically grown cells.Abbreviation CRP cyclic AMP receptor protein     

Mutant fs(1) 1163 of Drosophila melanogaster alters yolk protein secretion from the fat body

Summary The mutant fs(1) 1163 of Drosophila melanogaster, which was isolated by Gans et al. (1975) is a recessive homozygous female sterile at 18°C and a dominant female — sterile at 29°C. We reported previously that there are reduced quantities of the largest of the three yolk polypeptides in Drosophila melanogaster in the haemolymph and eggs of this mutant at 29°C (Bownes and Hames 1978 a). In this paper we show that the yolk protein defect maps within approximately 2.5 recombination units of the female sterility at 21±2.5 map units on the X-chromosome. The temperature-sensitive period of the yolk protein defect is after emergence. In vitro labelling of fs(1) 1163 ovaries and fat bodies showed that they were able to synthesise yolk polypeptide 1. Interestingly, studies on the proteins present in the various tissues indicate that the fat body tends to accumulate all three yolk polypeptides in the mutant. This phenotype is partially co-dominant in that an effect is seen in heterozygotes as well as homozygotes and is enhanced by increased temperature. This mutant could therefore have a defect (a) in the structural gene for yolk polypeptide 1, (b) in the processing and secretion enzyme systems; (c) in the fat body or all tissues leading to altered secretion properties.Mutants like fs(1) 1163 which alter specific steps in vitellogenesis should be of value for analysing the genetic and biochemical control of the synthesis, transport and sequestering of the yolk polypeptides during oogenesis.     

The yeast DNA polymerase-primase complex: Genes and proteins

The yeast DNA polymerase-primase complex is composed of four polypeptides designated p180, p74, p58 and p48. All the genes coding for these polypeptides have now been cloned. By protein sequence comparison we found that yeast DNA polymerase I (α) shares three major regions of homology with several DNA polymerases. A fourth region, called region P, is conserved in yeast and human DNA polymerase α. The site of a temperature-sensitive mutation in the POL1 gene which causes decreased stability of the polymerase-primase complex has been sequenced and falls in this region. We hypothesize that region P is important for protein—protein interactions. Highly selective biochemical methods might be similarly important to distinguish functional domains in the polymerase-primase complex. An autocatalytic affinity labeling procedure has been applied to map the active center of yeast DNA primase. From this approach we conclude that both primase subunits (p48 and p58) participate in the formation of the catalytic site of the enzyme.     

Isolation and Characterization of Mustard (Sinapis alba L.) Seed Storage Proteins

A total storage protein fraction was prepared from mustard (Sinapis alba L.) seeds via isolated protein bodies and characterized by sedimentation, immunological, and electrophoretic techniques. Mustard seed storage protein consists of three fractions (1) a “legumin-like” 13-S complex composed of two pairs of disulfide-linked polypeptides (16.5 + 28.5 kDa and 19.5 + 34 kDa, respectively) and two single polypeptides (18 kDa and 26 kDa), (2) a “vicilin-like” 9-S complex composed of two glycoproteins (64 kDa and 77 kDa), and (3) two small polypeptides (10 kDa and 11 kDa) which probably represent the 1.7-S complex found in other Cruciferae. In contrast to related species, no glycosylated polypeptide was found in the 13-S complex. Immunological relationships were found between the paired polypeptides of the 13-S complex but not between polypeptides of the 13-S complex and polypeptides of the 9-S complex. Pulse-chase labeling and in vitro translation of polysomal RNA from young embryos demonstrated that the polypeptides of the 13-S complex originate from high molecular mass precursors, except for the 18 kDa polypeptide which appears to be synthesized in its final size. The amino-acid composition of the major polypeptides of the mustard storage protein is given.     

Hardware and software in biology: Simultaneous origin of proteins and nucleic acids via hydrogen cyanide polymers

Hydrogen cyanide polymers—heterogeneous solids varying in color from yellow to orange to red to black—may be among the organic macromolecules most readily formed within the solar system. Current studies of these ubiquitous compounds point to the presence of polyamidine structures readily converted by water to polypeptides. Implications for prebiotic chemistry are profound. Primitive Earth may have been covered by HCN polymers as well as other organic compounds, either through bolide bombardment or by photochemical reactions in a reducing atmosphere. Membrane material—carboxylic acids, carbohydrates, polypeptides—accumulated in lakes and oceans, while in the absence of water, on land, polyamidines could have been the original dehydrating agents directing the synthesis of nucleosides and nucleotides from available sugars, phosphates and nitrogen bases. Most significant would have been the parallel synthesis of polypeptides and polynucleotides ariaing from the dehydrating action of polyamidines on nucleotides. Metabolic material—hardware—thus arose separately from genetic components—software—with subsequent interfacting producing the first replicating protocells.On our dynamic planet this polypeptide-polynucleotide symbiosis mediated by polyamidines may have set the pattern for the evolution of protein-nucleic acid systems controlled by enzymes, the mode characteristic of life today.     

Intermolecular cross-linking of vitelline envelope polypeptides predominates in the hardened sea urchin fertilization envelope

At fertilization, the sea urchin egg vitelline envelope (VE) elevates, and a subset of released cortical granule proteins, paracrystalline protein fraction (PCF), associates with the VE to form the fertilization envelope (FE). Cortical granule peroxidase cross-links FE polypeptides by phenolic coupling of tyrosyl residues. We have used an immunological approach to determine which polypeptides are linked together in the hardened FE of Strongylocentrotus purpuratus. Soluble polypeptides were extracted from hardened FEs, and antibodies were prepared in rabbits against the insoluble envelope matrix (FE ghost). Whole immune serum and purified IgGs each reacted with FE ghosts when using an enzyme-linked immunosorbent assay. VEs isolated by means of three published procedures cross-reacted with the immune serum and purified IgGs. Soluble FE polypeptides also cross-reacted with whole immune serum and IgGs owing to the presence of VE polypeptides. Hyalin, a protein not found in FEs, and PCF did not cross-react with antiserum against FE ghosts. To determine which VE polypeptides were cross-linked in the hardened FE, VE polypeptides were immunoblotted by using antiserum against FE ghosts. Most of the VE polypeptides that ranged from 68,000 to 283,000 molecular weight cross-reacted with the antibody.     

Purification and properties of two truncated endoglucanases produced in Escherichia coli harbouring Clostridium cellulolyticum endoglucanase gene celCCD

The endoglucanase gene, celCCD, of Clostridium cellulolyticum has been expressed in Escherichia coli. Multiple active polypeptides were detected in the E. coli cells. The relative molecular mass (M_r) of two major active polypeptides were 56 000 (D56) and 38 000 (D38), which were smaller than the deduced M_r of the mature protein (63 401). D56 and D38 were purified from the periplasmic fraction. The N-terminal sequences of the two purified polypeptides were identical to that of the mature endoglucanase (Ala-Ile-Asn-Ser-Gln-Asp-Met-Val---) deduced from the nucleotide sequence. These data indicated that these polypeptides were produced by processing the original mature protein in the C-terminal region. The enzymatic properties of these two polypeptides were very similar, except that the specific activity of D38 was 2–3.5-fold higher than that of D56, and D38 was more heat stable than D56. Correspondence to: T. Kodama     

Polypeptide compositions and NH2-terminal amino acid sequences of proteins in foxtail and proso millets

Seed protein of foxtail and proso millets were fractionated into polypeptides that were analyzed for their major protein, prolamin, and the NH2-terminal amino acid sequences of the proteins were determined. The proteins extracted from foxtail and proso millets were 64.1% and 80.0% prolamin, respectively. The polypeptides of the prolamins were classified into two groups. The major polypeptides of 27-19 kDa were rich in leucine and alanine, whereas the 17-14 kDa polypeptides were rich in methionine and cysteine. Glutelin-like proteins that were extracted with a reducing reagent were high in proline content, the major polypeptides being 17 and 20 kDa. The NH2-terminal amino acid sequence showed that the major polypeptides of prolamin were homologous to alpha-zein and a glutelin-like protein containing the Pro-Pro-Pro sequence, like the repetitive sequence of gamma-zein. Although the prolamin consisted of a similar subunit to that of zein, polypeptides with various pI values were found among them.     

Photocontrol of chloroplast and mitochondrial polypeptide levels in euglena

Two dimensional polyacrylamide gel electrophoresis resolved protein from intact chloroplasts of wild type Euglena gracilis Klebs var. bacillaris Cori into 185 polypeptides of which 55 were localized on the whole cell polypeptide map. Of these chloroplast polypeptides, the relative amounts of 49 increased, the relative amounts of two decreased, and the relative amounts of four polypeptides were unaltered by exposure of dark grown resting cells to light for 72 hours. Proteins from intact purified mitochondria obtained from a bleached mutant (W₁₀BSmL) lacking plastids were resolved into 193 polypeptides of which 44 were localized on the whole cell polypeptide map from wild type cells. Of these mitochondrial polypeptides, the relative amount of one increased, the relative amounts of 12 were unaltered, and the relative amounts of 31 decreased after exposure of the dark grown resting cells to light. Since it is known that the development of the chloroplast in Euglena occurs without a net increase in total cellular protein and without a change in the size of the cellular amino acid pools, the degradation of mitochondrial polypeptides represents a major source of amino acids for the synthesis of chloroplast polypeptides.