The identification and characterisation of an actin-binding site in alpha-actinin by mutagenesis.

We have shown previously that the N-terminal actin-binding domain of alpha-actinin retains activity when expressed in E. coli as a fusion protein with glutathione-S-transferase. In the present study we have made a series of N- and C-terminal deletions within this domain and show that an actin-binding site is contained within residues 120-134. Amino acid substitutions within this region indicate that several highly conserved hydrophobic residues are involved in binding to F-actin. The hypothesis that the interaction between alpha-actinin and F-actin is predominantly hydrophobic in nature is supported by the observation that binding is relatively independent of salt concentration.