Chickpea seed proteins: Modification during germination

Changes in the proteins of chickpea during a 12-day germination period are reported using techniques of gel filtration, DEAE-cellulose chromatography, polyacrylamide gel (PAG) electrophoresis and ultracentrifugation. In the ultracentrifuge, the total proteins of dormant seeds resolve into 3 components which have the sedimentation coefficients of 2.2 S, 6.9 S and 10.3 S respectively. On germination, the presence of fractions of lower sedimentation coefficient indicates possible degradation of these components; in the early stages, the degradation rate of the 7 S fraction is higher, while the 10 S fraction is broken down faster in the later stages. Gel filtration experiments indicate the possibility of degradation of high polymer into intermediary products. Increase in the relative mobility of protein components on PAG and elution constant on DEAE-cellulose chromatographs indicates an increase in the net negative charge of the protein fractions. The accumulation of subunits of the proteins is negligible during the germination period.     

Charakterisierung extrazellulärer proteine und enzyme aus pektinkulturfiltraten von Botrytis cinerea

Extracellular proteins from Botrytis cinerea CBS 144.55 were separated by use of isoelectric focusing in polyacrylamide gel and thin layer isoelectric focusing. In addition to the protein pattern, the activities of protease, amylase, cellulase, polygalacturonase, pectinesterase and glycosidases were determined.     

Stereospecificity of peptide transport by germinating barley embryos

The stereospecific requirements for peptide transport in the scutellum of germinating barley (Hordeum vulgare) embryos are described. Replacement of an L-amino acid residue in a peptide by its D-stereoisomer decreases the affinity of the peptide for the transport site, leading to a reduction in transport. Substitution of a second D-residue reduces affinity still further. The extent to which transport is inhibited depends upon the position of the D-residue in the primary sequence, with D-residues at the C-terminus of the peptide having the greatest effect. Competition between D- and L-peptides indicates that they both enter via the same transport system. Although D-amino acids can be accumulated when presented as a peptide, these same D-residues are not transported when supplied as the free amino acids. L-Leu-D-leu is accumulated intact against a concentration gradient, indicating the operation of an active transport mechanism that can function without the involvement of peptidase activity.     

Association of spectrin with its membrane attachment site restricts lateral mobility of human erythrocyte integral membrane proteins

Interactions between spectrin and the inner surface of the human erythrocyte membrane have been implicated in the control of lateral mobility of the integral membrane proteins. We report here that incubation of “leaky” erythrocytes with a water-soluble proteolytic fragment containing the membrane attachment site for spectrin achieves a selective and controlled dissociation of spectrin from the membrane, and increases the rate of lateral mobility of fluorescein isothiocyanate-labeled integral membrane proteins (> 70% of label in band 3 and PAS-1). Mobility of membrane proteins is measured as an increase in the percentage of uniformly fluorescent cells with time after fusion of fluorescent with nonfluorescent erythrocytes by Sendai virus. The cells are permeable to macromolecules since virus-fused erythrocytes lose most of their hemoglobin. The membrane attachment site for spectrin has been solubilized by limited proteolysis of inside-out erythrocyte vesicles and has been purified (V). Bennett, J Biol Chem 253:2292 (1978). This 72,000-dalton fragment binds to spectrin in solution, competitively inhibits association of ³²P-spectrin with inside-out vesicles with a K_i of 10^?7M, and causes rapid dissociation of ³²P-spectrin from vesicles. Both acid-treated 72,000-dalton fragment and the 45,000 dalton-cytoplasmic portion of band 3, which also was isolated from the proteolytic digest, have no effect on spectrin binding, release, or membrane protein mobility. The enhancement of membrane protein lateral mobility by the same polypeptide that inhibits binding of spectrin to inverted vesicles and displaces spectrin from these vesicles provides direct evidence that the interaction of spectrin with protein components in the membrane restricts the lateral mobility of integral membrane proteins in the erythrocyte.     

Immunocytochemical location of vitellin in the egg of the silkworm,Bombyx mori,during early developmental stages

Summary Vitellin was purified from eggs of the silkworm,Bombyx mori, by a new method in which vitellin was extracted from isolated yolk granules. The purified vitellin had a molecular weight of 540,000. An antibody against purified vitellin was prepared in rabbits. It reacted with the hemolymph vitellogenin as well as with purified vitellin, but not with other proteins in the hemolymph or in the extract from yolk granules. The anti-vitellin IgG was used to immunocytochemically locate vitellin in theBombyx non-diapause egg during early developmental stages. In the egg, just after oviposition, vitellin was located in internal yolk granules and in small yolk granules of the periplasm. During the early developmental stages studied, vitellin was not metabolized uniformly throughout the egg. The vitellin of the internal yolk granules located at the posterior-dorsal part and of the small peripheral yolk granules was utilized in 16 h and 2 days, respectively, after oviposition. A thin, very vitellin-poor layer was located between the periplasm and the vitellin-rich interior in the newly laid egg. it was always in close contact with the periphery where blastoderm and germ-band cells developed.     

Effect of the sequences upstream from the ribosome-binding site on the yield of protein from the cloned gene for phage MS2 coat protein

The translational efficiency of the coat protein gene of phage MS2 has been examined in vivo with respect to neighbouring sequences. The cloned MS2 DNA has been gradually shortened starting at the 5' or 3' terminus, and its effect on coat protein synthesis monitored. Removal of the 3'-terminal sequences had little influence. In contrast, the gradual removal of the 5'-terminal region profoundly reduces translation. Long before the ribosomal binding site (RBS) of the coat protein (CP) gene is reached, the yield of CP has dropped by one order of magnitude. Functional half-lives of the various messengers were found not to be significantly different. Available evidence indicates that the secondary structure of the RBS in native and shortened MS2 RNA is identical. We infer that important determinants for ribosome recognition lie 5' to the RBS region of the MS2 RNA coat gene.     

Gene fusion vectors based on the gene for staphylococcal protein A

Two plasmid vectors, containing the gene coding for staphylococcal protein A and adapted for gene fusion, have been constructed. These vectors will allow fusion of any gene to the protein A gene, thus giving hybrid proteins which can be purified, in a one-step procedure, by IgG affinity chromatography. As an example of the practical use of such vectors, the protein A gene has been fused to the lacZ gene of Escherichia coli. E. coli strains containing such plasmids produce hybrid proteins with both IgG binding and β-galactosidase activities. The hybrid protein(s) can be immobilized on IgG-Sepharose by its protein A moiety with high efficiency without losing its enzymatic activity and they can be eluted from the column by competitive elution with pure protein A. The fused protein(s) also binds to IgG-coated microtiter wells which means that the in vivo product can be used as an enzyme conjugate in ELISA tests.     

Fermented foods, feeds and beverages

There has been a proliferation of books and papers dealing with the indigenous fermented foods/beverages of the world. It is anticipated that these foods/beverages will play an ever-increasingly important role in feeding both the developing and the developed world as population increases from approximately 4.5 billion to 6 billion by the year 2000 and to 8 to 12 billion people in the 21st century. The indigenous fermented foods consist of microbial protein grown on edible substrates. Microbial or single cell protein (SCP) per se continues to receive research and development attention. It is likely to play an important role in feeding animals in the future when it becomes competitive with soy protein. It may play a direct role in feeding humans in the future after its safety for feeding animals has been adequately demonstrated and it has been shown that it can be processed into foods acceptable to humans. At the present time, mushrooms, a form of microbial protein highly acceptable to humans, which can be grown readily on ligno-cellulosic and other agricultural and food processing wastes, offer considerable opportunity for expanding man's food supply.     

Light-dependent conformational change at rhodopsin's cytoplasmic surface detected by increased susceptibility to proteolysis

Rhodopsin in bovine photoreceptor disk membranes was subjected to limited proteolysis by thermolysin, removing twelve amino acids from rhodopsin's carboxyl terminus. (1) The rate of proteolysis is significantly faster with rhodopsin following exposure to light than with unbleached rhodopsin, provided that the incubation conditions (pH, temperature) favor the formation of metarhodopsin II. (2) If the disk membranes are illuminated under conditions in which metarhodopsin I is the predominant photoproduct (pH 8.5, 0°C), no increase in the rate of proteolysis is observed compared to unilluminated membranes. (3) The light-induced increase in the rate of proteolysis is transient: it slowly decays in the dark to the original rate found for unbleached rhodopsin. The enhanced susceptibility to proteolysis appears to measure a conformational change at rhodopsin's cytoplasmic surface which is first exhibited at the metarhodopsin II stage. This and possibly other light-dependent changes may allow rhodopsin to mediate its signal as a light-receptor protein by binding to and activating certain rod cell enzymes.     

The oxidation-reduction kinetics of the reaction of cytochrome c1 with non-physiological redox agents

The kinetics of the oxidation-reduction reactions of cytochrome c₁ with ascorbate, ferricyanide, triphenanthrolinecobalt(III) and N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD) have been examined using the stopped-flow technique. The reduction of ferricytochrome c₁ by ascorbic acid is investigated as a function of pH. It is shown that at neutral and alkaline pH the reduction of the protein is mainly performed by the doubly deprotonated form of ascorbate. From the ionic-strength-dependence studies of the reactions of cytochrome c₁ with ascorbate, ferricyanide and triphenanthrolinecobalt(III), it is demonstrated that the reaction rate is governed by electrostatic interactions. The second-order rate constants for the reaction of cytochrome c₁ with ascorbate, ferricyanide, TMPD and triphenanthrolinecobalt(III) are 1.4·10⁴, 3.2·10³, 3.8·10⁴ and 1.3·10⁸ M^?1·s^?1 (pH 7.0, I = 0, 10°C), respectively. Application of the Debye-Hückel theory to the the ionic-strength-dependence studies of these redox reactions of cytochrome c₁ yielded for ferrocytochrome c₁ and ferricytochrome c₁ a net charge of ?5 and ?4, respectively. The latter value is close to that of ?3 for the oxidized enzyme, calculated from the amino acid sequence of the protein. This implies that not a local charge on the surface of the protein, but the overall net charge of cytochrome c₁ governs the reaction rate with small redox molecules.