Molecular Interplay of Murein Synthases and Murein Hydrolases inEscherichia coli

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Abstract
Affinity chromatography using different lytic transglycosylases as a specific ligand revealed an interaction of both murein hydrolases and murein synthases. This interaction is taken as evidence for the assemblage into a multienzyme complex that could function as a murein replicase precisely copying the given three-dimensional structure of the murein sacculus. The sacculus of the mother cell would function as a template, which is identically replicated by copying the lengths of the existing glycan strands and the pattern of crosslinkages. A hypothetical enzyme complex specifically involved in cell division and a complex specifically involved in cell elongation are presented. It is postulated that PBPs 1a and/or 1b are present in both complexes, whereas the presence of PBP2 or PBP3 defines the specificity of the murein-synthesizing machinery as being involved in either cell elongation or septation. Moreover, the proposed "holoenzyme" suprastructure could explain why the specific inhibition of PBPs 1a/1b results in bacteriolysis and why inhibition of PBP2 and PBP3 causes the well-known morphological alterations, spherical growth, and filamentation, respectively.