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J. Bacteriol., Dec 1996, 7106-7111, Vol 178, No. 24
MR Baquero, M Bouzon, JC Quintela, JA Ayala and F Moreno
In the course of a study of genes located at min 44 of the Escherichia coli
genome, we identified an open reading frame with the capacity to encode a
43-kDa polypeptide whose predicted amino acid sequence is strikingly
similar to those of the well-known DD-carboxipeptidases penicillin-binding
proteins PBP5 and PBP6. The gene product was shown to bind
[3H]benzylpenicillin and to have DD-carboxypeptidase activity on
pentapeptide muropeptides in vivo. Therefore, we called the protein PBP6b
and the gene dacD. As with other E. coli DD-carboxypeptidases, PBP6b is not
essential for cell growth. A quadruple dacA dacB dacC dacD mutant was
constructed and shown to grow as well as its isogenic wild- type strain,
indicating that the loss of any known PBP-associated DD- carboxypeptidase
activity is not deleterious for E. coli. We also identified the homologous
gene of dacD in Salmonella typhimurium as one of the components of the
previously described phsBCDEF gene cluster.
Copyright © 1996, American Society for Microbiology
dacD, an Escherichia coli gene encoding a novel penicillin-binding protein (PBP6b) with DD-carboxypeptidase activity
Unidad de Genetica Molecular, Hospital Ramon y Cajal, Madrid, Spain.
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