A survey of a functional amino acid of class C beta-lactamase corresponding to Glu166 of class A beta-lactamases.
The class C beta-lactamase of Citrobacter freundii GN346 is a typical cephalosporinase comprising 361 amino acids. The aspartic acid at position 217 and glutamic acid at position 219 in this beta-lactamase were, respectively, previously shown not to be the counterpart of Glu166 (ABL166) in class A beta-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 Glu166 through sequence alignment based on other criteria, the glutamic acids at positions 195 and 205 in the class C beta-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 beta-lactamase lacks a functional acidic residue corresponding to Glu166 in class A enzymes.
Nukaga
M
M
Division of Microbial Chemistry, Faculty of Pharmaceutical Sciences, Chiba University, Japan.
Tanimoto
K
K
Tsukamoto
K
K
Imajo
S
S
Ishiguro
M
M
Sawai
T
T
D000409:Alanine / Q000737:chemistry; D000595:Amino Acid Sequence; D001483:Base Sequence; D017931:DNA Primers; D004926:Escherichia coli / Q000737:chemistry; D005971:Glutamates / Q000737:chemistry*; D018698:Glutamic Acid; D005973:Glutamine / Q000737:chemistry; D008239:Lysine / Q000737:chemistry; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017386:Sequence Homology, Amino Acid; D001618:beta-Lactamases / Q000737:chemistry*
D017931:DNA Primers; D005971:Glutamates; D005973:Glutamine; D018698:Glutamic Acid; D001618:beta-Lactamases; D008239:Lysine; D000409:Alanine