title: Nucleotide sequences of the pbpX genes encoding the penicillin-binding proteins 2x from Streptococcus pneumoniae R6 and a cefotaxime-resistant mutant, C506.
abstract: Development of penicillin resistance in Streptococcus pneumoniae is due to successive mutations in penicillin-binding proteins (PBPs) which reduce their affinity for beta-lactam antibiotics. PBP2x is one of the high-Mr PBPs which appears to be altered both in resistant clinical isolates, and in cefotaxime-resistant laboratory mutants. In this study, we have sequenced a 2564 base-pair chromosomal fragment from the penicillin-sensitive S. pneumoniae strain R6, which contains the PBP2x gene. Within this fragment, a 2250 base-pair open reading frame was found which coded for a protein having an Mr of 82.35kD, a value which is in good agreement with the Mr of 80-85 kD measured by SDS-gel electrophoresis of the PBP2x protein itself. The N-terminal region resembled an unprocessed signal peptide and was followed by a hydrophobic sequence that may be responsible for membrane attachment of PBP2x. The corresponding nucleotide sequence of the PBP2x gene from C504, a cefotaxime-resistant laboratory mutant obtained after five selection steps, contained three nucleotide substitutions, causing three amino acid alterations within the beta-lactam binding domain of the PBP2x protein. Alterations affecting similar regions of Escherichia coli PBP3 and Neisseria gonorrhoeae PBP2 from beta-lactam-resistant strains are known. The penicillin-binding domain of PBP2x shows highest homology with these two PBPs and S. pneumoniae PBP2b. In contrast, the N-terminal extension of PBP2x has the highest homology with E. coli PBP2 and methicillin-resistant Staphylococcus aureus PBP2'. No significant homology was detected with PBP1a or PBP1b of Escherichia coli, or with the low-Mr PBPs.
authors.affiliation: Max-Planck Institut für Molekulare Genetik, Berlin, FRG.
authors.forename: G
authors.initials: G
authors.lastname: Laible
authors.forename: R
authors.initials: R
authors.lastname: Hakenbeck
authors.forename: M A
authors.initials: MA
authors.lastname: Sicard
authors.forename: B
authors.initials: B
authors.lastname: Joris
authors.forename: J M
authors.initials: JM
authors.lastname: Ghuysen
mesh_terms: D000595:Amino Acid Sequence; D019881:Aminoacyltransferases; D001426:Bacterial Proteins; D001483:Base Sequence; D002352:Carrier Proteins / Q000032:analysis / Q000235:genetics*; D002439:Cefotaxime / Q000378:metabolism*; D004352:Drug Resistance, Microbial / Q000235:genetics; D029968:Escherichia coli Proteins; D006602:Hexosyltransferases; D008969:Molecular Sequence Data; D002267:Muramoylpentapeptide Carboxypeptidase / Q000032:analysis / Q000235:genetics*; D009154:Mutation; D046915:Penicillin-Binding Proteins; D010406:Penicillins / Q000378:metabolism; D046928:Peptidoglycan Glycosyltransferase; D010458:Peptidyl Transferases; D015183:Restriction Mapping; D012689:Sequence Homology, Nucleic Acid; D046929:Serine-Type D-Ala-D-Ala Carboxypeptidase; D013296:Streptococcus pneumoniae; D014170:Transformation, Genetic
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D046915:Penicillin-Binding Proteins; D010406:Penicillins; D019881:Aminoacyltransferases; C478701:penicillin-binding protein 2b, Streptococcus; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D046928:Peptidoglycan Glycosyltransferase; C478681:penicillin-binding protein 1B, E coli; D046929:Serine-Type D-Ala-D-Ala Carboxypeptidase; D002267:Muramoylpentapeptide Carboxypeptidase; D002439:Cefotaxime