Binding of penicillin to thiol-penicillin-binding protein 3 of Escherichia coli: identification of its active site.
In order to determine the active site of penicillin-binding protein 3 of Escherichia coli (PBP3), the serine residue at position 307 was replaced with alanine, threonine or cysteine by oligonucleotide-directed site-specific mutagenesis. Since a unique BanII site exists at the position corresponding to serine-307, BanII digestion of the plasmid DNA after mutagenesis resulted in significant enrichment of the mutant plasmids. For mutagenesis, the gene coding for PBP3 ( ftsI) was inserted into the expression cloning vector pIN-IIB. The hybrid protein produced was able to bind penicillin while mutant PBP3 in which serine-307 was replaced with either alanine or threonine did not lead to any detectable binding. However, contrary to the report of Broome-Smith et al. (1985) thiol-penicillin-binding protein 3, in which serine-307 was replaced with cysteine, was still able to bind penicillin. Replacement of serine-445 with an alanine residue had no effect on penicillin binding to PBP3.[1]References
- Binding of penicillin to thiol-penicillin-binding protein 3 of Escherichia coli: identification of its active site. Houba-Hérin, N., Hara, H., Inouye, M., Hirota, Y. Mol. Gen. Genet. (1985) [Pubmed]
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