Molecular domain structure of porcine vinculin and metavinculin

Summary Metavinculin is a higher molecular weight variant of vinculin expressed only in cardiac and smooth muscle. Using microsequencing methods on the intact molecules and their proteolytic subfragments we have been able to map the common and different parts of these closely related proteins. Both vinculin and metavinculin, from mammals and birds exhibit a relatively protease resistant 90 kD core fragment. N-terminal sequencing analysis of the avian and mammalian core fragments as well as of major core subfragments obtained by extended proteolysis placed the core domain at the N-terminus of the intact molecules and revealed identity between metavinculin and vinculin as well as between species. Limited chymotryptic digestion of porcine vinculin and metavinculin yielded a common 16 kD fragment which could be placed at the C-terminus of the cDNA sequence derived from chick fibroblast vinculin (G. J.Price, P.Jones, M. D.Davison, R.Bendori, S.Griffiths, B.Patel, B.Geiger and D. R.Critchley 1988, in press). From additional sequence data the metavinculin specific fragment could be placed at the metavinculin C-terminus. Using a polyclonal antibody specific for porcine metavinculin a peptide unique to metavinculin could be identified. Direct sequencing of this, as well as of related, overlapping fragments, purified by reversed phase HPLC revealed a 68 amino acid insert in procine metavinculin, between the core fragment and the C-terminal piece, common to vinculin and metavinculin. The domain organizazions of vinculin and metavinculin and their possible functional implications are discussed.Abbreviations SDS sodium dodecyl sulfate - EDTA ethylendinitrilotetra acetic acid - HPLC high pressure liquid chromatography