Calpain 1 behaviour toward cytoskeletal targets was inves-tigated using twoa-actinin isoforms from smooth and skel-etal muscles. These two isoforms which are, respectively, sensitiveandresistant tocalpaincleavage, interactwiththe protease when usinginvitro binding assays. The stability of the complexes in EGTA [Kd(–Ca2+)¼ ± ] was improved in the presence of 1 mMcalcium ions [Kd(+Ca2+)¼ ± ]. Location of the binding structures shows that the C-terminal domain ofa-actinin and each calpain subunit, 28 and 80 kDa, participates in the interaction
