title: Alterations in penicillin-binding protein 2B from penicillin-resistant wild-type strains of Streptococcus pneumoniae.
abstract: The 1.5-kb transpeptidase-encoding region (TER) of penicillin-binding protein (PBP) 2B was amplified and sequenced from 18 penicillin-resistant isolates of Streptococcus pneumoniae, with each isolate representing a different DNA fingerprint profile of the TER. PBP 2B TERs from penicillin-resistant isolates revealed extensive sequence divergence from the penicillin-susceptible R6 strain, differing by up to 170 nucleotide substitutions and resulting in up to 38 alterations in the amino acid sequence of the protein. All penicillin-resistant isolates showed sequence divergence within a +/- 300-bp area at the center of the PBP 2B TER. Although a number of amino acid substitutions were found within this central area of PBP 2B, only two substitutions were common to all resistant isolates, namely, Thr-252 replacement by Ala and Glu-282 replacement by Gly. These two substitutions appear to be essentially associated with a decreased affinity of PBP 2B for penicillin. A second block of divergent nucleotide sequence was prominent amongst isolates with high levels of resistance. This was a +/- 100-bp area of the TER around nucleotide 1300 and included the substitution of Gly for Asp-431, which was the only amino acid substitution within this area that was common to all isolates. These data may assist in the definition of the structural changes in the penicillin-binding site of PBP 2B associated with penicillin resistance in S. pneumoniae.
authors.affiliation: Department of Medical Microbiology, School of Pathology, South African Institute for Medical Research, Johannesburg.
authors.forename: A M
authors.initials: AM
authors.lastname: Smith
authors.forename: K P
authors.initials: KP
authors.lastname: Klugman
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D001483:Base Sequence; D002352:Carrier Proteins; D006602:Hexosyltransferases / Q000737:chemistry* / Q000235:genetics; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000737:chemistry* / Q000235:genetics; D002267:Muramoylpentapeptide Carboxypeptidase; D010403:Penicillin Resistance; D046915:Penicillin-Binding Proteins; D010458:Peptidyl Transferases / Q000737:chemistry* / Q000235:genetics; D013296:Streptococcus pneumoniae / Q000737:chemistry* / Q000187:drug effects
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D009097:Multienzyme Complexes; D046915:Penicillin-Binding Proteins; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D002267:Muramoylpentapeptide Carboxypeptidase