Residues 1-35 of NcTnI, including the phosphorylatable serines 22 and 23, are positioned over the NcTnC domain (Figures ). Addressing first the phosphorylation independent interactions, we find that the NcTnI is anchored on TnC, near the N-terminal end by interactions between NcTnI Arg9 and the Glutamines 15 and 19 of NcTnC, which are the start of cTnC helix A (orange circle, Figure ).