The overall structure and model quality of the Tse3–Tsi3 complex. (a) Ribbon diagram showing the binary complex, in which Tse3 is coloured yellow and Tsi3 cyan. The Ca2+ ions present in Tse3 are represented by magenta balls. (b) Representative 2Fobs − Fcalc density map contoured at 1.0σ of the interface between Tse3 and Tsi3. The protein stick model is coloured by element: carbon, yellow (Tse3) or cyan (Tsi3); oxygen, red; nitrogen, blue.