TALIN CAN CROSS-LINK ACTIN-FILAMENTS INTO BOTH NETWORKS AND BUNDLES

The talin-actin interaction was examined by using negative staining an d cosedimentation assays. At pH 6.4 and low ionic strength, talin exte nsively crosslinked actin filaments into both networks and bundles. Th e bundles consist of parallel actin filaments with a center-to-center distance of 13 nm, and talin crossbridges spaced at 36-nm intervals al ong the bundles. As pH was increased stepwise from 6.4 to 7.3, talin's bundling activity was decreased first, then its networking activity. Qualitatively similar results were obtained at pH 6.4 by increasing io nic strength. Chemical crosslinking indicated talin was present as a d imer from pH 6.4 to 7.3, with or without added KC1. The results show t hat talin can interact directly with actin filaments by formation of a ctin filament networks and bundles, with the bundles more sensitive to dissolution by increase in pH or ionic strength. (C) 1996 Academic Pr ess, Inc.