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A survey of a functional amino acid of class Cβ‐lactamase corresponding to Glu 166 of class A β‐lactamases
Author(s) -
Nukaga Michiyoshi,
Tanimoto Kyoko,
Tsukamoto Kikuo,
Imajo Seiichi,
Ishiguro Masaji,
Sawai Tetsuo
Publication year - 1993
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(93)80491-c
Subject(s) - glutamine , glutamic acid , alanine , aspartic acid , enzyme , lysine , amino acid , residue (chemistry) , chemistry , stereochemistry , biochemistry
The class C β‐lactamase of Cltrobacter freundii GN346 is a typical cephalosporinase comprising 361 amino acids. The aspartic acid at position 217 and glutamic acid at position 219 in this β‐lactamase were, respectively, previously shown not to be the counterpart of Glu 166 (ABL166) in class A β‐lactamases, even though sequence alignment of class A and C enzymes strongly suggested this possibility [(1990) FEBS Lett. 264, 211‐214; (1990) J. Bacteriol. 172, 4348‐4351]. We tried again to assign candidates for the counterpart of Glu 166 through sequence alignment based on other criteria, the glutamic acids at positions 195 and 205 in the class C β‐lactamase being selected. To investigate this possibility, these two glutamic acids were changed to glutamine, lysine or alanine, respectively. All the mutant enzymes showed more than 50% of the activity of the wild‐type enzyme, indicating that the possibility was ruled out. These results strongly suggested the possibility that the class C β‐lactamase lacks a functional acidic residue corresponding to Glu 166 in class A enzymes.