SEQUENCE-ANALYSIS AND EVOLUTIONARY PERSPECTIVES OF ROB-1 BETA-LACTAMASE

The nucleotide sequence of the ROB-1 β-lactamase gene from Haemophilus influenzae plasmid R(Rob) was determined. The structural gene encodes a polypeptide of 305 amino acids, with an estimated molecular mass of 30,424 for the mature form of the protein. The ROB-1 gene showed low homologies with other β-lactamases at the nucleic acid level. By using two statistical computer methods, assessment of the extent of similarity between ROB-1 and other known β-lactamase amino acid sequences suggested that ROB-1 is a class A enzyme. Alignment of class A β-lactamases with ROB-1 identified conserved residues. The use of a mutation matrix for detecting distance relationships indicated that ROB-1 has higher values and homologies with β-lactamases of gram-positive bacteria, giving insight into its ancestry and divergence.