Studies of the high molecular weight penicillin-binding proteins of Bacillus subtilis.

G Kleppe,J.L Strominger

doi:10.1016/s0021-9258(17)30091-1

Abstract

Seven or eight penicillin-binding proteins (PBPs) were detected in Bacillus subtilis membranes. By introducing covalent affinity chromatography employing cephalosporins as ligands, milligram amounts of three high molecular weight PBPs (PBP 1 ab, Mr = 120,000; PBP 2b, Mr = 94,000; and PBP 4, Mr = 78,000) were obtained without any contamination of the major PBP 5, the D-alanine carboxypeptidase. Small amounts of pure PBP 2b could be isolated by manipulation of the affinity chromatography conditions. Structural and physical properties of these proteins as well as the generation of one major penicilloyl peptide from each PBP by digestion with pepsin suggest that each PBP is the product of a separate gene. No enzymatic activity could be found in mixtures of these high molecular weight PBPs employing substrates used for the transpeptidase and D-alanine carboxypeptidase assays in particulate membrane fractions.

Highlights

Seven or eight penicillin-binding proteins (PBPs) were detected in Bacillus subtilis membranes
The demonstration of multiple penicillin-binding proteins in the bacterial membranes indicated a more complex killing mechanism in which more than one protein/enzyme could be the target for the lethal action of p-lactam antibiotics [4]
This idea is based on the assumption that each of the PBPs’ found in the membrane is an enzyme which is irreversibly inhibited by the formation of a covalent bond to these antibiotics [5]

Summary

Introduction

Seven or eight penicillin-binding proteins (PBPs) were detected in Bacillus subtilis membranes. It has been suggested that p-lactam antibiotics kill bacteria by inhibiting transpeptidation, the terminal enzymatic reaction in the synthesis of the bacterial peptidoglycan [1, 2]. The demonstration of multiple penicillin-binding proteins in the bacterial membranes indicated a more complex killing mechanism in which more than one protein/enzyme could be the target for the lethal action of p-lactam antibiotics [4]. This idea is based on the assumption that each of the PBPs’ found in the membrane is an enzyme which is irreversibly inhibited by the formation of a covalent bond to these antibiotics [5]

Methods

Results

Conclusion