We report the complete primary structure of chicken embryo vinculin. The amino acid sequence was derived from the nucleotide sequence of five overlapping cDNA clones isolated from a Agtll phage library. Chicken embryo vinculin contains 1066 amino acids, has a calculated Mr of 116,990, a calculated pI of 5.9, and a hydropathy index of -4.22. A search of the National Biomedical Research Foundation protein sequence data base found no proteins with significant homology to vinculin. A striking feature of the linear sequence is a proline-rich region extending between residues 837 and 879. This region contains 45% proline and 19% aspartic plus glutamic acids; it is also the longest hydrophilic stretch in the molecule. The proline-rich region separates an amino-terminal domain with a calculated pI of 5.4 from a carboxyl-terminal domain with a calculated pI of 9.7. This feature suggests a structural basis for the specific interaction of vinculin with acidic phospholipids and a mechanism for the shuttling of vinculin between cytoplasm and membrane-associated junctional plaque.Vinculin, a 130-kDa protein, is one of the few identified components of microfilament-associated cell junctions (1). Because these cell-cell and cell-substrate junctions play key roles in growth and morphogenesis, definition of the events regulating the assembly of vinculin into the junctional plaque is an important goal. The distribution of vinculin between cytoplasm and junctional plaque varies depending on cell contact (2, 3), developmental stage (4), viral transformation (5), and stimulation with certain growth hormones (6, 7). A variety ofbiochemical observations have been made that may lead to a molecular understanding of the dynamics of vinculin assembly at adherens junctions. Among these are the in vitro interaction of vinculin with talin (8), a-actinin (9, 10), and acidic phospholipids (11,12); myristoylation (13) and transformation-sensitive palmitoylation of vinculin (14); phosphorylation of vinculin both in vitro (11,15)

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