title: Vinculin tail conformation and self-association is independent of pH and H906 protonation.
abstract: Vinculin is a highly conserved cytoskeletal protein that localizes to sites of cell adhesion. The tail domain of vinculin (Vt) forms tight autoinhibitory interactions with the head domain and down-regulates vinculin function by obscuring ligand binding sites. Ligand binding is required for both vinculin activation and function, and one of vinculin's primary roles as a cell adhesion protein involves its ability to link the Actin cytoskeleton to the cell membrane. Vt can bind F-Actin and phosphoinositol 4,5-bisphosphate, and association with these ligands has been reported to cause a conformational change in Vt. Moreover, a single histidine residue, H906, was reported to be critical for both a pH dependent conformational change and pH dependent self-association. In this study, we investigate the role of pH on Vt structure and self-association. In contrast to earlier observations, our studies do not support a significant alteration in Vt conformation over this pH range. Moreover, while we identify a site of Vt dimerization, similar to that observed previously by X-ray crystallography, the weak K(d) (approximately 300 microM) determined for Vt self-association does not differ significantly between pH 5.5 and pH 7.5.
authors.affiliation: Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.
authors.forename: Sean M
authors.initials: SM
authors.lastname: Palmer
authors.forename: Michael D
authors.initials: MD
authors.lastname: Schaller
authors.forename: Sharon L
authors.initials: SL
authors.lastname: Campbell
mesh_terms: D000818:Animals; D002645:Chickens; D006639:Histidine / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D009154:Mutation; D011485:Protein Binding; D011487:Protein Conformation; D011522:Protons; D016596:Vinculin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D011522:Protons; D016596:Vinculin; D006639:Histidine