Stoichiometry of covalent actin-subfragment 1 complexes formed on reaction with a zero-length cross-linking compound.

The interaction of actin and rabbit subfragment 1 has been reexamined by using a carbodiimide cross-linking reagent. A major doublet with an apparent molecular weight of 134 000 as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis has been identified. A minor product of much higher molecular weight is also formed. Stoichiometry determinations using [3H]actin and [14C]subfragment 1 indicate that the major doublet is a 1:1 complex of actin and subfragment 1. This result confirms that reported by Sutoh (1983) [ Sutoh , K. (1983) Biochemistry 22, 1579-1585]