Crystallization and preliminary X-ray analysis of the Ca²⁺-bound C-terminal lobe of troponin C in complex with a troponin I-derived peptide fragment from Akazara scallop

Recombinant TnC was expressed in Escherichia coli, purified, complexed with a 24-residue synthetic peptide derived from scallop troponin I (TnI) and crystallized. Troponin C (TnC) is the Ca²⁺-binding component of troponin and triggers muscle contraction. TnC of the invertebrate Akazara scallop can bind only one Ca²⁺ at the C-terminal EF-hand motif. Recombinant TnC was expressed in Escherichia coli, purified, complexed with a 24-residue synthetic peptide derived from scallop troponin I (TnI) and crystallized. The crystals diffracted X-rays to 1.80 Å resolution and belonged to space group P2₁2₁2₁, with unit-cell parameters a = 32.1, b = 42.2, c = 60.0 Å. The asymmetric unit was assumed to contain one molecular complex of the Akazara scallop TnC C-lobe and TnI fragment, with a Matthews coefficient of 1.83 ų Da⁻¹ and a solvent content of 33.0%