The sorcin-annexin VII calcium-dependent interaction requires the sorcin N-terminal domain

Surface plasmon resonance experiments show that at neutral pH the stability of the complex between sorcin and annexin VII (synexin) increases dramatically between 3 and 6 microM calcium; at the latter cation concentration the K(D) value is 0.63 microM. In turn, the lack of complex formation between the sorcin Ca(2+) binding domain (33-198) and synexin maps the annexin binding site to the N-terminal region of the sorcin polypeptide chain. Annexin VII likewise employs the N-terminal domain, more specifically the first 31 amino acids, to interact with sorcin [Brownawell, A.M. and Creutz, C.E. (1997) J. Biol. Chem. 272, 22182-22190]. The interaction may involve similar structural motifs in the two proteins, namely GGYY and GYGG in sorcin and GYPP in synexin.