The calcium-induced switch in the troponin complex probed by fluorescent mutants of troponin I

作者：Oliveira DCSG; Reinach FC^*

来源：European Journal of Biochemistry, 2003, 270(14): 2937-2944.

DOI：10.1046/j.1432-1033.2003.03659.x

• 5-hydroxytryptophan
• Ca-2+-binding protein
• fluorescence
• troponin
• skeletal muscle

The Ca2+ -induced transition in the troponin complex (Tn) regulates vertebrate striated muscle contraction. Tn was reconstituted with recombinant forms of troponin I (TnI) containing a single intrinsic 5-hydroxytryptophan (5HW). Fluorescence analysis of these mutants of TnI demonstrate that the regions in TnI that respond to Ca2+ binding to the regulatory N-domain of TnC are the inhibitory region (residues 96-116) and a neighboring region that includes position 121. Our data confirms the role of TnI as a modulator of the Ca2+ affinity of TnC; we show that point mutations and incorporation of 5HW in TnI can affect both the affinity and the cooperativity of Ca2+ binding to TnC. We also discuss the possibility that the regulatory sites in the N-terminal domain of TnC might be the high affinity Ca2+ -binding sites in the troponin complex.

• 出版日期2003-7