Nucleotide sequences of the pbpX genes encoding the penicillin-binding proteins 2x from Streptococcus pneumoniae R6 and a cefotaxime-resistant mutant, C506

Mol Microbiol. 1989 Oct;3(10):1337-48. doi: 10.1111/j.1365-2958.1989.tb00115.x.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Aminoacyltransferases*
  • Bacterial Proteins*
  • Base Sequence
  • Carrier Proteins / analysis
  • Carrier Proteins / genetics*
  • Cefotaxime / metabolism*
  • Drug Resistance, Microbial / genetics
  • Escherichia coli Proteins*
  • Hexosyltransferases*
  • Molecular Sequence Data
  • Muramoylpentapeptide Carboxypeptidase / analysis
  • Muramoylpentapeptide Carboxypeptidase / genetics*
  • Mutation
  • Penicillin-Binding Proteins
  • Penicillins / metabolism
  • Peptidoglycan Glycosyltransferase*
  • Peptidyl Transferases*
  • Restriction Mapping
  • Sequence Homology, Nucleic Acid
  • Serine-Type D-Ala-D-Ala Carboxypeptidase*
  • Streptococcus pneumoniae
  • Transformation, Genetic


  • Bacterial Proteins
  • Carrier Proteins
  • Escherichia coli Proteins
  • Penicillin-Binding Proteins
  • Penicillins
  • Aminoacyltransferases
  • penicillin-binding protein 2b, Streptococcus
  • Peptidyl Transferases
  • Hexosyltransferases
  • Peptidoglycan Glycosyltransferase
  • penicillin-binding protein 1B, E coli
  • Serine-Type D-Ala-D-Ala Carboxypeptidase
  • Muramoylpentapeptide Carboxypeptidase
  • Cefotaxime

Associated data

  • GENBANK/X16367