3-dimensional organization of the N-terminal vinculin head fragment

The cytoskeleton-associated protein vinculin is composed of a globular head and an elongated tail domain. The protein can he cleaved by V8 protease tr eatment into two fragments with apparent molecular masses of 90 and 29/27 k Da, respectively. So far, no high-resolution data on the tertiary structure of the N-terminal 90-kDa fragment are available. We analyzed the 90-kDa fr agment in detail, using electron spectroscopic imaging in conjunction with modelling experiments, The front view projection of this fragment appears r oughly rhomboidal, with 4 intensity maxima arranged at the vertices and a s tain-filled region in the center. Based on a detailed examination of differ ent particle projections, a 3-dimensional model was constructed which appea rs as a flattened tetrahedron, A comparison of the 90-kDa fragment with the intact protein allows for a correlation between the subdomain organization of the vinculin head and the biochemically defined V8 protease cleavage si tes (aa 851 and 857),