Fig. 1.

A schematic representation of the interactions between components of cardiac thin filament (A) and the Ca²⁺-bound form of the troponin core complex from cardiac muscle (B). A, The Ca²⁺-dependent interactions between TnI, TnC, TnT and actin are shown in solid double-headed arrows. Ip, TnI inhibitory peptide; Sp, TnI switch peptide. The interaction between cardiac specific NTnI and NTnC in the presence of Ca²⁺ occurs when Ser23/Ser24 of NTnI are unphosphorylated. B, structure of the cardiac Tn core complex contains TnC (red, grey) and parts of TnI (blue) and TnT (gold). Bifunctional rhodamine (BR) probes cross-linked cysteines along either the N, A, B, C, E, F or G helix of TnC (red). BR probes cross-linking cysteines across either N and A, or F and G helices are shown in yellow dumbbells. D helix which is inaccessible is in grey.