Vinculin is a 117 kDa microfilament-associated protein located at the cytoplasmic aspects of focal contacts and cell-cell adherens type junctions. In both sites, vinculin participates in the formation of a submembrane xxxplaquexxx structure which is responsible for the attachment of actin filaments to the plasma membrane. Vinculin consists of 1066 amino acids, which form a large 90 kDa globular head domain and a rod-like 29 kDa tail domain. The two domains are separated by several stretches of proline residues where the major proteolytic cleavage sites are located. The experimental procedure for isolation and purification of vinculin from smooth muscle has been developed and crystals of native vinculin suitable for X-ray analysis have been obtained. The homogeneity of the vinculin solution was analyzed prior to crystallization using dynamic light scattering. Crystals of vinculin have been obtained in buffer containing 2 mg ml(-1) protein, 0.9 M ammonium sulfate, 0.1 M MES pH 6.5 using both the hanging-drop and sitting-drop vapour-diffusion methods. The crystals have the form of rhombic plates and grow to maximal dimensions of 0.3 x 0.3 x 0.05 mm in two weeks. Preliminary X-ray data show that the crystals diffract to 3.5 Angstrom resolution at the X11 beamline of DESY and belong to the monoclinic space group P2(1). Crystal unit-cell parameters are estimated to be a = 57, b = 351, c = 70 Angstrom, alpha = 90, beta = 113, gamma = 90 degrees.
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