The NMR structure of domain C2 of human cardiac Myosin Binding Protein C
[MYPC3_HUMAN] Defects in MYBPC3 are the cause of familial hypertrophic cardiomyopathy type 4 (CMH4) [MIM:115197]. Familial hypertrophic cardiomyopathy is a hereditary heart disorder characterized by ventricular hypertrophy, which is usually asymmetric and often involves the interventricular septum. The symptoms include dyspnea, syncope, collapse, palpitations, and chest pain. They can be readily provoked by exercise. The disorder has inter- and intrafamilial variability ranging from benign to malignant forms with high risk of cardiac failure and sudden cardiac death.                   
[MYPC3_HUMAN] Thick filament-associated protein located in the crossbridge region of vertebrate striated muscle a bands. In vitro it binds MHC, F-actin and native thin filaments, and modifies the activity of actin-activated myosin ATPase. It may modulate muscle contraction or may play a more structural role.
Publication Abstract from PubMed
Myosin-binding protein C (MyBP-C) binds to myosin with two binding sites, one close to the N terminus and the other at the C terminus. Here we present the solution structure of one part of the N-terminal binding site, the third immunoglobulin domain of the cardiac isoform of human MyBP-C (cC2) together with a model of its interaction with myosin. Domain cC2 has the beta-sandwich structure expected from a member of the immunoglobulin fold. The C-terminal part of the structure of cC2 is very closely related to telokin, the myosin binding fragment of myosin light chain kinase. Domain cC2 also contains two cysteines on neighboring strands F and G, which would be able to form a disulfide bridge in a similar position as in telokin. Using NMR spectroscopy and isothermal titration calorimetry we demonstrate that cC2 alone binds to a fragment of myosin, S2Delta, with low affinity (kD = 1.1 mM) but exhibits a highly specific binding site. This consists of the C-terminal surface of the C'CFGA' beta-sheet, which includes Glu(301), a residue mutated to Gln in the disease familial hypertrophic cardiomyopathy. The binding site on S2 was identified by a combination of NMR binding experiments of cC2 with S2Delta containing the cardiomyopathy-linked mutation R870H and molecular modeling. This mutation lowers the binding affinity and changes the arrangement of side chains at the interface. Our model of the cC2-S2Delta complex gives a first glimpse of details of the MyBP-C-myosin interaction. Using this model we suggest that most key interactions are between polar amino acids, explaining why the mutations E301Q in cC2 and R870H in S2Delta could be involved in cardiomyopathy. We expect that this model will stimulate future research to further refine the details of this interaction and their importance for cardiomyopathy.
Dissecting the N-terminal myosin binding site of human cardiac myosin-binding protein C. Structure and myosin binding of domain C2.,Ababou A, Gautel M, Pfuhl M J Biol Chem. 2007 Mar 23;282(12):9204-15. Epub 2006 Dec 27. PMID:17192269
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.