Kinetic determination of focal adhesion protein formation

I examined the binding kinetics between integrin (alpha(IIb)beta(3)) and pu rified focal adhesion proteins, including alpha-actinin, filamin, vinculin, talin, and F-actin. Using static light-scatter technique, I observed affin ities of the order talin > filamin > F-actin > alpha-actinin > (talin when bound to vinculin) which were lower when integrin was complexed with fibron ectin. No binding between integrin and vinculin was detected. The calculate d dissociation constants (K-d) ranged between 0.4 mu M and 5 mu M. These re sults in part confirm previously published data using different methods. Th e modest affinity with which the focal adhesion proteins interact in vitro might be indicative of how cells, e.g., thrombocytes, gain a high degree of versatility and velocity. (C) 2000 Academic Press.