DIFFERENTIAL ACTIN ORGANIZATION BY VINCULIN ISOFORMS - IMPLICATIONS FOR CELL-TYPE-SPECIFIC MICROFILAMENT ANCHORAGE

Vinculin is found in all adherens junctions, while metavinculin, a lar ger splice variant, is coexpressed with vinculin only in smooth and ca rdiac muscle. To understand the significance of metavinculin expressio n, we compared ligand binding between turkey vinculin and metavinculin , Residues 1-258 mere found essential for head-tail interactions in bo th proteins. The tail domains (VT and MVT, respectively) both bind to F-actin, However, while VT bundles F-actin, MVT generates highly visco us F-actin webs. In transfected PtK2 cells, VT causes F-actin needles or coils, while MVT-expressing cells display a diffuse F-actin distrib ution, Thus, the MVT-specific insert induces an F-actin supraorganizat ion different from the VT-based form, suggesting that metavinculin has a specific role in muscle. (C) 1998 Federation of European Biochemica l Societies.