The high resolution crystal structure for class A beta-lactamase PER-1 reveals the bases for its increase in breadth of activity.
The treatment of infectious diseases by beta-lactam antibiotics is continuously challenged by the emergence and dissemination of new beta-lactamases. In most cases, the cephalosporinase activity of class A enzymes results from a few mutations in the TEM and SHV penicillinases. The PER-1 beta-lactamase was characterized as a class A enzyme displaying a cephalosporinase activity. This activity was, however, insensitive to the mutations of residues known to be critical for providing extended substrate profiles to TEM and SHV. The x-ray structure of the protein, solved at 1.9-A resolution, reveals that two of the most conserved features in class A beta-lactamases are not present in this enzyme: the fold of the Omega-loop and the cis conformation of the peptide bond between residues 166 and 167. The new fold of the Omega-loop and the insertion of four residues at the edge of strand S3 generate a broad cavity that may easily accommodate the bulky substituents of cephalosporin substrates. The trans conformation of the 166-167 bond is related to the presence of an aspartic acid at position 136. Selection of class A enzymes based on the occurrence of both Asp(136) and Asn(179) identifies a subgroup of enzymes with high sequence homology.
Tranier
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S
Groupe de Cristallographie Biologique, Institut de Pharmacologie et de Biologie Structurale du CNRS, 205 route de Narbonne, F-31077 Toulouse cedex, France.
Bouthors
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AT
Maveyraud
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L
Guillet
V
V
Sougakoff
W
W
Samama
J P
JP
D000595:Amino Acid Sequence; D002510:Cephalosporinase / Q000378:metabolism; D003198:Computer Simulation; D018360:Crystallography, X-Ray / Q000379:methods; D004926:Escherichia coli / Q000201:enzymology; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D001618:beta-Lactamases / Q000737:chemistry* / Q000378:metabolism*
D011994:Recombinant Proteins; D002510:Cephalosporinase; C108863:beta-lactamase PER-1; D001618:beta-Lactamases