Bacterial peptidoglycan binds to tubulin

A search for cellular binding proteins for peptidoglycan (PGN), a CD14- and TLR2-dependent macrophage activator from Grampositive bacteria, using PGN- affinity chromatography and N-terminal micro-sequencing, revealed that tubu lin was a major PGN-binding protein in mouse macrophages. Tubulin also co-e luted with PGN from anti-PGN vancomycin affinity column and bound to PGN co upled to agarose. Tubulin-PGN binding was preferential under the conditions that promote tubulin polymerization, required macromolecular PGN, was comp etitively inhibited by soluble PGN and tubulin, did not require microtubule -associated proteins, and had an affinity of 100-150 nM. By contrast, bindi ng of tubulin to lipopolysaccharide (LPS) had 2-3 times lower affinity, fas ter kinetics of binding, and showed positive cooperativity. PGN enhanced tu bulin polymerization in the presence of 4 M glycerol, but in the absence of glycerol, both PGN and LPS decreased microtubule polymerization. These res ults indicate that tubulin is a major PGN-binding protein and that PGN modu lates tubulin polymerization. (C) 2000 Elsevier Science B.V. All rights res erved.