Transmission of the Ca2+-regulatory signal in skeletal muscle thin filaments

Studies dealing with some aspects of the thin-filament based regulatory mechanism of striated muscle are discussed. A key event is a Ca2+-induced shift of TnI from a binding site on actin to TnC, as indicated by optical and crosslinking experiments. The regions concerned involve residues 1-12 in actin, residues 96-116 in TnI, and residues 89-100 in TnC. These changes in interaction are accompanied by changes in TnC and TnI that occur on a millisecond time scale which is consistent with their being part of the regulatory processes underlying regulation in vivo.