Yeast Derivatives Research Articles

N epsilon,N epsilon-dimethyl-lysine cytochrome c as an NMR probe for lysine involvement in protein-protein complex formation.

The reductively dimethylated derivatives of horse and yeast iso-1-ferricytochromes c have been prepared and characterized for use as NMR probes of the complexes formed by cytochrome c with bovine liver cytochrome b5 and yeast cytochrome c peroxidase. The electrostatic properties and structures of the derivatized cytochromes are not significantly perturbed by the modifications; neither are the electrostatics of protein-protein complex formation or rates of interprotein electron transfer. Two-dimensional 1H-13C NMR spectroscopy of the complexes formed by the derivatized cytochromes with cytochrome b5 and cytochrome c peroxidase has been used to investigate the number and identity of lysine residues of cytochrome c that are involved in interprotein interactions of cytochrome c. The NMR data are incompatible with simple static models proposed previously for the complexes formed by these proteins, but are consistent with the presence of multiple, interconverting complexes of comparable stability, consistent with studies employing Brownian dynamics to model the complexes. The NMR characteristics of the Nepsilon,Nepsilon-dimethyl-lysine groups, their chemical shift dispersion, oxidation state and temperature dependences and the possibility of chemical exchange phenomena are discussed with relevance to the utility of Nepsilon, Nepsilon-dimethyl-lysine's being a generally useful derivative for characterizing protein-protein complexes.

5451413 Yeast derivative and method to improve bread quality : Fok Jacob J; Hille Jan D R; Van Der Veen Beren Delft, Netherlands assigned to Gist-Brocades B V

5451413 Yeast derivative and method to improve bread quality : Fok Jacob J; Hille Jan D R; Van Der Veen Beren Delft, Netherlands assigned to Gist-Brocades B V

5451413 Yeast derivative and method to improve bread quality : Fok Jacob J; Hille Jan D R; Van Der Veen Beren Delft, Netherlands assigned to Gist-Brocades B V

5451413 Yeast derivative and method to improve bread quality : Fok Jacob J; Hille Jan D R; Van Der Veen Beren Delft, Netherlands assigned to Gist-Brocades B V

Electron transfer in cytochrome c depends upon the structure of the intervening medium.

Long-distance electron-transfer (ET) reactions through proteins are involved in a great many biochemical processes; however, the way in which the protein structure influences the rates of these reactions is not well understood. We have therefore measured the rates of intramolecular ET from the ferroheme to a bis(2,2'-bipyridine)imidazoleruthenium(III) acceptor at histidine 39 or 54 in derivatives of yeast iso-1-cytochrome c, and studied the effect of an asparagine to isoleucine mutation at position 52, a residue situated between the heme and the electron acceptor. The Fe2+-->Ru3+ rate constants demonstrate that residue 52 affects ET from the heme to His54 (Ile52 > Asn52), but not to His39 (Ile52 = Asn52). The enhanced Fe(2+)-Ru3+(His54) electronic coupling for the N52I/K54H protein is in good agreement with sigma-tunneling calculations, which predict the length of the ET pathways between the heme and His54. The structure of the intervening medium between the heme and electron acceptors at the protein surface influences the donor-acceptor couplings in cytochrome c.

Mutagenic and recombinogenic consequences of DNA-repair inhibition during treatment with 1,3-bis(2-chloroethyl)-1-nitrosourea in Saccharomyces cerevisiae

The yeast Saccharomyces cerevisiae has been used as a model system to explore whether the clinical combination of the antitumour agent BCNU (1,3-bis(2-chloroethyl)-1-nitrosourea) with DNA-repair inhibitors would affect the drug's mutagenic or recombinogenic potential. Preliminary experiments suggested that mitotic crossing-over and other mutagenic events are controlled in a separate fashion. BCNU was more toxic in yeast derivatives with specific defects in any of the three recognized major DNA repair pathways than in the DNA-repair-proficient parent strain. However, in a diploid homozygous for rad18, BCNU showed enhanced mutagenic and recombinogenic potential. Both of these effects were reduced in a comparable rad3 strain, and mitotic crossing-over but not other types of mutagenic event eliminated in the rad52 derivative. Experiments were performed in the presence of three DNA-repair inhibitors which are currently in clinical use and might by available for combination chemotherapy. Hydroxyurea and amsacrine themselves caused mitotic crossing-over and other events, and did not reduce mutagenic or recombinogenic potential of the BCNU. Hydroyurea actually decreased toxicity of the BCNU. Caffeine, however, showed some effect in enhancing toxicity and decreasing both mutagenic and recombinogenic potential of the drug. Development of more specific repair inhibitors related to amsacrine or to caffeine, using these repair-deficient strains as model systems, might lead to an enhanced clinical potential of this bisalkylating drug and related compounds.

Interaction of the “back” of yeast iso-1-cytochrome c with yeast cytochrome c oxidase

The 102-S-(2-thiopyridyl) and 102-S-(4-azidophenacyl) derivatives of yeast iso-1-cytochrome c have been prepared, both containing one mole of label per mole of cytochrome c. When the 102-S-(2-thiopyridyl) cytochrome c is allowed to interact with purified, detergent-solubilized yeast cytochrome oxidase, covalent crosslinked products are formed containing 0.9 to 0.98 moles of cytochrome c per oxidase. When the 102-S-(4-azidophenacyl) cytochrome c is exposed to the oxidase in the presence of ultraviolet light, covalently crosslinked products containing 0.2 to 0.35 moles of cytochrome c per oxidase are formed. SDS-polyacrylamide gel electrophoresis of these crosslinked products reveals the formation of a new band of apparent molecular weight 38,000 Daltons and the concurrent disappearance of subunit III (a crosslink of subunit III and cytochrome c). These affinity and photoaffinity crosslinking results are interpreted as evidence that the “backside” of yeast iso-1-cytochrome c interacts with subunit III of yeast cytochrome oxidase.

Substrate specificity of three different extracellular proteolytic enzymes from Staphylococcus aureus

The proteolytic specificities of three different extracellular proteinases from Staphylococcus aureus have been determined. Carboxymethylated derivatives of yeast and horse liver alcohol dehydrogenases were used as substrates. Protease I had the most selective specificity, cleaving mainly peptide bonds at the carboxy-terminal side of a single type of residue, glutamic acid. Protease II had the broadest specificity with no clear preferential cleavages of particular peptide bonds, but with extensive proteolytic activity. Protease III had a rather broad specificity, cleaving at the amino-terminal side of hydrophobic residues. The enzymes resemble different types of other known proteinases and their combined effect is great and probably of importance for growth and virulence of S. aureus.

Cordycepin sensitivity in adenosine utilizing mutants of Saccharomyces cerevisiae

Saccharomyces cerevisiae is resistant to the antibiotic cordycepin (3′-deoxyadenosine), an adenosine analogue which inhibits nucleic acid synthesis in bacteria. To obtain cordycepin-sensitive derivatives of yeast we mutagenized an adenine-requiring strain and selected clones able to utilize adenosine in place of adenine; wild type yeast strains normally cannot satisfy their adenine requirement with adenosine. The adenosine-utilizing mutants we obtained were very sensitive to cordycepin (50 % inhibition of growth at 11.5 μg/ml). In sensitive mutants the drug rapidly inhibited RNA and DNA synthesis, but only affected protein synthesis after a lag. Both the ability to use adenosine and cordycepin sensitivity were recessive to the adenosine non-utilizing, drug resistant phenotype.

Food Flavor

In closing the world's protein gap, flavor con trol is a vital factor. Food primarily must be nu tritious to sustain life, but unless the flavor is acceptable to the human palate, it may not be eaten. Today, new ways are being found to up grade natural foods lacking flavor and to add flavor in new man-made meat substitutes having a high nutritive content. Flavor chemistry is the newest branch of food chemistry in the United States. Gas chrom atograph y, whereby food flavor volatiles can be separated into their manifold chemical com ponents, is being perfected. Other physico chemical techniques are also being used to identify these chemicals, but with the help of the human nose and brain which are more sen sitive than mechanical devices, New and improved synthetic fruit flavors have already been developed as there are not enough natural fruits grown to meet the demand for these flavors in foods. Similarly, beef extract is being replaced with flavor potentiators: MSG (monosodium glutamate); HVP (hydrolyzed plant proteins); and the flavor nucleotides-5' IMP (inosine 5' monophosphate) that occurs in meat and fish muscle, and 5' GMP (guanosine 5' monophosphate), which is produced biochem ically from yeast and yeast derivatives. Progress has been made with meat substitutes. Natural flavorings derived from beef, chicken and ham have been combined with soy, yeast or algae protein to make simulated meats.

QUANTITATIVE STUDIES ON INCREASED POTENCY OF LIVER EXTRACT BY INCUBATION WITH NORMAL HUMAN GASTRIC JUICE

Excerpt The therapeutic effectiveness of liver and fractions of liver in the treatment of pernicious anemia is well established. Minot, Cohn, Murphy, and Lawson1demonstrated that although slight re...