Affinity chromatography as a means to study multienzyme complexes involved in murein synthesis.

The interaction of murein hydrolases and synthases was studied by affinity chromatography. The lytic transglycosylases Slt70 and MltB of E. coli were purified and covalently linked to CNBr-activated Sepharose. Membrane extracts were analyzed for proteins that interact with the immobilized murein hydrolases. Slt70-Sepharose was found to retain the PBPs 1b, 1c, 2, and 3. Likewise MltB-Sepharose enriched PBP 1b, 1c, and 3. Thus both lytic transglycosylases have an affinity for a transpeptidase, PBP2 and/or 3, as well as for the bifunctional transpeptidase/transglycosylase 1b. Interestingly, in addition, the poorly characterized PBP 1c interacts strongly with both Slt70 and MltB. It is speculated that the lytic transglycosylases assemble a multienzyme complex consisting of hydrolases and synthases, which is involved in growth of the stress-bearing murein sacculus.