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Biomedical subjects

R Bracha

Publications and source records attributed to R Bracha.

54 records · Page 3Linked to original sources
PubMed1978

Defect in biosynthesis of the linkage unit between peptidoglycan and teichoic acid in a bacteriophage-resistant mutant of Staphylococcus aureus.

The biosynthesis of the linkage region between peptidoglycan and the ribitol teichoic acid was investigated in the bacteriophage-resistant, teichoic acid-less mutant Staphylococcus aureus 52A5 (Chatterjee et al., J. Bacteriol. 100:846--853, 1969). Membrane preparations of this strain were found to be incapable of forming the first intermediate of the biosynthetic pathway, namely, the transfer of N-acetyl-D-glucosamine (GlcNAc) from UDP-GlcNAc to the acceptor molecule, which presumbably is undecaprenol phosphate (R. Bracha and L. Glaser, Biochem. Biophys. Res. Commun. 72:1091--1098, 1976). The addition of heat-inactivated membrane preparations of S. aureus 52A2 (which normally has ribitol teichoic acid) that had been preincubated with UDP-GlcNAc to membranes of strain 52A5 enabled the synthesis of teichoic acid. These data suggest that the mutational defect in the teichoic acid-less organism is in the synthesis of the first compound of the linkage unit, and this is apparently the reason for its absence in the cell walls.

Cell Wall↗
PubMed1976

In vitro system for the synthesis of teichoic acid linked to peptidoglycan.

A crude cell wall preparation from Staphylococcus aureus H prepared by the method of Mirelman and Sharon (1972) was shown to catalyze the synthesis of polyribitol phosphate linked to the cell wall peptidoglycan. The reaction used cytidine diphosphate (CDP)-ribitol as a substrate and in addition required the presence of CDP-glycerol, uridine diphosphate (UDP)-N-acetyl-D-glucosamine, and adenosine triphosphate. Incubation of radioactive CDP-glycerol with the crude cell wall preparation resulted in the transfer of glycerol phosphate residues to the cell wall; this reaction was greatly stimulated by the presence of UDP-N-acetylglucosamine. These data suggest that polyribitol phosphate is linked to the cell wall peptidoglycan by an oligomer contaning N-acetyl-D-glucosamine and glycerol phosphate.

Adenosine Triphosphate↗
PubMed1974

Effect of penicillin on the in vivo formation of the D-alanyl-L-alanine peptide cross-linkage in cell walls of Micrococcus luteus.

Penicillin G was found to inhibit the formation of the d-alanyl-l-alanine cross-linkage in intact cells of Micrococcus luteus. This reaction was approximately 50-fold less susceptible to penicillin than the formation of the d-alanyl-l-lysine cross-linkage in the same organism. The presence of two penicillin-susceptible transpeptidation reactions that function in the incorporation of peptidoglycan precursors into the cell wall is proposed.

Alanine↗
PubMed1972

Role of the penicillin-sensitive transpeptidation reaction in attachment of newly synthesized peptidoglycan to cell walls of Micrococcus luteus.

Cell-wall preparations of Micrococcus luteus (lysodeikticus) catalyze in vitro peptidoglycan synthesis from UDP N-acetyl-D-glucosamine, UDP N-acetylmuramic acid-pentapeptide, and glycine. Newly synthesized peptidoglycan is partially cross-linked by a transpeptidation reaction with concomitant release of C-terminal D-alanine. Penicillin not only strongly inhibits release of D-alanine (98% at 1 mug/ml), but also markedly inhibits incorporation of acetylglucosamine and N-acetylmuramic acid-pentapeptide into the preformed cell-wall peptidoglycan. The simplest explanation for the results is that incorporation of newly synthesized strands of peptidoglycan and their attachment to "older" cell-wall peptidoglycan proceeds mainly by transpeptidation and that transglycosylation is responsible only for part of the elongation of the pre-existing peptidoglycan. Another possibility is that incorporation occurs by transglycosylation, but it cannot continue without concurrent formation of peptide cross-bridges.

Amino Acids↗