Evidence for a ternary interaction between alpha-actinin, (meta)vinculin and acidic-phospholipid bilayers.
The cytoskeletal component vinculin has been demonstrated by hydrophobic photoradiolabelling, to insert into bilayers containing acidic phospholipids and trace amounts of a photoactivatable analogue of lecithin. It is shown in this study that the higher-molecular-mass variant metavinculin and alpha-actinin, also share this property. alpha-Actinin and vinculin were also shown to associate with phosphatidylserine liposomes by chromatography of protein/lipid mixtures on a Bio-Gel A-5m column. Furthermore, interesting differences in the behaviour of binary mixtures of these proteins, in the presence of phosphatidylserine liposomes, are shown. Thus, incubation of alpha-actinin with vinculin or metavinculin, prior to the addition of liposomes, strongly inhibited the photoradiolabelling of alpha-actinin under conditions in which the liposome surface was non-limiting, but enhanced the labelling of vinculin. In contrast, vinculin and metavinculin did not mutually influence their labelling. Using gel-filtration chromatography, it was shown that alpha-actinin still bound to the vinculin-liposome complex, under conditions similar to those used for hydrophobic photolabelling with a non-limiting lipid surface. In the presence of limiting amounts of liposomes, the alpha-actinin/vinculin ratio was markedly decreased in the liposome fractions. Our results suggest the formation of a ternary complex consisting of vinculin, alpha-actinin and phospholipids. In this complex, both proteins interact at the bilayer, resulting in an altered conformation of the two proteins and, as a consequence, in modified bilayer interactions.
Niggli
V
V
Department of Pathology, University of Bern, Switzerland.
Gimona
M
M
D000185:Actinin / Q000032:analysis / Q000737:chemistry*; D000818:Animals; D002850:Chromatography, Gel; D008051:Lipid Bilayers / Q000737:chemistry*; D008081:Liposomes / Q000032:analysis; D009124:Muscle Proteins / Q000737:chemistry*; D010743:Phospholipids / Q000737:chemistry; D013552:Swine; D016596:Vinculin / Q000032:analysis / Q000737:chemistry*
D008051:Lipid Bilayers; D008081:Liposomes; D009124:Muscle Proteins; D010743:Phospholipids; D000185:Actinin; D016596:Vinculin