An arginine residue at the active site of beta-lactamase from Shigella flexneri UCSF-129
Campos, M.; Alarcón, M.A.; González, H.; Carvajal, N.
Microbios 73(294): 37-43
1993
ISSN/ISBN: 0026-2633 PMID: 8441355 Document Number: 420319
The role of a residue of arginine at the active site of beta-lactamase from Shigella flexneri UCSF-129 was studied. It is a local pathogenic strain which produces intestinal problems, especially in children. Purified enzymes were obtained by affinity chromatography on phenylboronic acid-agarose gels. The enzyme was serine dependent with a molecular weight of 23.6 kD. It was specifically modified with phenylglyoxal (1/830 molar ratio) and incubated for 20 min in the presence of 50 mM sodium phosphate buffer at pH 8.3. The chemical change was established by isoelectric focusing, since a loss of one positive charge was detected. Protection by cephradine, a substance, indicated the presence of a residue of arginine at its active site. Controls were conducted by differential spectroscopy. Similar results were obtained with 2,3-butanedione. This vital arginine stabilizes the negative charge of the carboxylic group of C-3 or C-4 from the substrates.