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G R Drapeau

Publications and source records attributed to G R Drapeau.

34 records · Page 2Linked to original sources
PubMed1976

Purification and properties of the alpha2beta2 complex of tryptophan synthetase of Proteus mirabilis.

A procedure is described for the purification of the tryptophan synthetase alpha2beta2 complex from cell extracts of Proteus mirabilis. A 30-fold purification was achieved with an overall yield of about 23% and a specific activity of 1,600. The complex can be dissociated and the subunits isolated in a pure form. The complex can be reconstituted from the isolated subunits to regain the initial activity. The alpha and beta2 subunits of the tryptophan synthetase complex of P. mirabilis are not significantly different from those of Escherichia coli and other enteric bacteria as to their physical properties, amino acid compositions, and enzymic properties. Complementation studies indicate that the alpha subunit of P. mirabilis hybridizes well with the beta2 subunit from E. coli. Similarly, the beta2 subunit of P. mirabilis readily complexes with the alpha subunits from E. coli, Salmonella typhimurium, and Serratia marcescens. The hybrids formed are all effective in catalyzing the conversion of indoleglycerol phosphate plus serine into tryptophan and glyceraldehyde 3-phosphate. However, these hybrids have reduced or no activity in the other reactions, namely, the condensation of indole and serine to form tryptophan or the aldolytic cleavage of indoleglycerol phosphate.

Escherichia coli↗
PubMed1975

Proton magnetic resonance titration curves of the three histidine residues of staphylococcal protease.

Proton magnetic resonance spectra of staphylococcal protease, a serine protease from Staphylococcus aureus, strain V8, are presented. Initial proton spectra were obtained at 220 MHz, and more detailed studies of the aromatic region were carried out by correlation spectroscopy at 250 MHz. The overall spectrum bears a close resemblance to one calculated from the sum of spectra of the component amino acids. Chemical shifts of the three tyrosine, four phenylalanine, and three histidine residues appear to be equivalent at pH 3.7 and 8.5 indicating that they are all in normal chemical environments in the enzyme. The staphylococcal protease contains a large number of slowly exchanging protons. In fact, interpretable spectra of the aromatic region were obtained only after extensive exchange of N-H groups with deuterium from the D2O solvent. Proton magnetic resonance titration studies of the three histidine residues indicate that these have normal chemical shifts and pK' values. When the data are fitted to single noninteracting titration curves, the histidine pK' values are 7.19 plus or minus 0.02, 6.85 plus or minus 0.03, and 6.69 plus or minus 0.02. The titration curves of two of the histidine residues indicate negative cooperativity. A possible explanation for this is a direct electrostatic interaction between the two histidines. The titration data for these histidines give a significantly better fit to such a mutual interaction model than to noninteracting titration curves. The component microscopic dissociation constants have been calculated. Mutual interaction leads to pK' displacements of 0.31 unit; which indicates a distance of approximately 7 angstrom between the two interacting histidine rings according to the model of Tanford and Roxby. The proton resonances of the two interacting histidines are doubled in the pH region 6.7-7.0 suggesting the presence of two forms of the enzyme having lifetimes in excess of 30 msec.

Amino Acids↗
PubMed1972

Staphylococcal protease: a proteolytic enzyme specific for glutamoyl bonds.

An extracellular protease of Staphylococcus aureus, strain V8, previously shown to cleave specifically the peptide bonds on the carboxyl-terminal side of either aspartate or glutamate residues in phosphate buffer (pH 7.8) hydrolyzes only glutamoyl bonds in either ammonium bicarbonate (pH 7.8) or ammonium acetate (pH 4.0). Of all aspartoyl bonds tested, only the Asp-Gly linkage is cleaved at a detectable rate. The staphylococcal protease hydrolyzes all of the seventeen different glutamoyl bonds studied, although those involving hydrophobic aminoacid residues with bulky side chains are cleaved at a lower rate.

Amino Acid Sequence↗
PubMed1972

Partial characterization of phosphoribosyl transferase, phosphoribosyl anthranilate isomerase, and indole glycerol phosphate synthase from Serratia marcescens.

The molecular organization of the enzymes phosphoribosyl (PR) transferase, phosphoribosyl anthranilate (PRA) isomerase, and indole glycerol phosphate (InGP) synthase of the tryptophan biosynthetic pathway of Serratia marcescens was investigated and compared with that reported in other enteric bacteria. PRA isomerase and InGP synthase activities were found to reside in a single polypeptide chain, a situation analogous to that in Escherichia coli, Salmonella typhimurium, and Aerobacter aerogenes. This bifunctional enzyme was purified to near homogeneity. Its molecular weight was estimated to be 48,000. PR transferase was found unassociated with PRA isomerase and InGP synthase after gel filtration and ion-exchange chromatography. Whereas in other enteric organisms PR transferase has been reported to form an aggregate with anthranilate synthase, it is a distinct entity in S. marcescens.

Cell-Free System↗
PubMed1966

Nutrition and metabolism of marine bacteria. XV. Relation of Na+-activated transport to the Na+ requirement of a marine pseudomonad for growth.

Drapeau, Gabriel R., (McGill University, Montreal, Quebec, Canada), Tibor I. Matula, and Robert A. MacLeod. Nutrition and metabolism of marine bacteria. XV. Relation of Na(+)-activated transport to the Na(+) requirement of a marine pseudomonad for growth. J. Bacteriol. 92:63-71. 1966.-A marine pseudomonad was found to require 50 to 100 mm Na(+) for maximal rate of oxidation of d-galactose and for the transport of d-fucose-H(3) into the cells. The same organism required 150 to 200 mm Na(+) for the oxidation of l-alanine and for the transport of phi-aminoisobutyric acid-C(14) (AIB-C(14)) into the cells. Competition studies indicated that d-galactose and d-fucose on the one hand and l-alanine and AIB on the other shared common carriers for transporting the compounds into the cells. This parallelism in Na(+) response for oxidation and transport extended to growth when l-alanine was the sole carbon source in the medium. When d-galactose was the sole carbon source, an amount of Na(+) equal to that with l-alanine was needed. KCN and dinitrophenol but not ouabain inhibited the uptake of AIB-C(14) by the cells. K(+) in addition to Na(+) was required for transport, and both Mg(++) and either Cl(-) or Br(-) were stimulatory. Photobacterium fischeri was also found to require Na(+) specifically for the uptake of AIB-C(14) by the cells.

Alanine↗