The interface between MyBP-C and myosin: site-directed mutagenesis of the CX myosin-binding domain of MyBP-C.

摘要: Myosin-binding protein-C (MyBP-C or C-protein) is a ca. 130 kDa protein present in the thick filaments of all vertebrate striated muscle. The contains ten domains, each 90-100 amino acids; seven are members IgI family proteins, three fibronectin type III family. motifs arranged following order (from N- to C-terminus): Ig-Ig-Ig-Ig-Ig-Fn-Fn-Ig-Fn-Ig. C-terminal Ig motif (domain X CX) its light meromyosin-binding site. A recombinant form CX, beginning at Met-1027, exhibits saturable binding myosin with an affinity comparable 13 chymotryptic fragment native MyBP-C. To identify surface CX involved interaction myosin, nine site-directed mutants (R37E, K43E, N49D, E52R, D56K, R73E, R74E, G80D and R103E) were constructed. Using new assay for assessing meromyosin (LMM) portion we demonstrate that just as full-length protein, able facilitate LMM polymerization. Moreover, show residues Arg-37, Glu-52, Asp-56, Arg-73, Arg-74 this rod. All these acids interact negatively charged LMM, since R37E, R73E R74E unable bind whereas E52R D56K higher than wild-type CX. Residues Lys-43 Arg-103 small but significant influence on reaction; Asn-49 Gly-80 seem not be interaction. Based data, model proposed between MyBP-C filaments. In model, interacts four molecules different sites thus explaining effects critical concentration