Format

Send to

Choose Destination
See comment in PubMed Commons below
J Biol Chem. 2013 Jul 26;288(30):21496-505. doi: 10.1074/jbc.M113.474346. Epub 2013 Jun 19.

A gain-of-function mutation in the M-domain of cardiac myosin-binding protein-C increases binding to actin.

Author information

1
University of California, Davis, California 95618, USA.

Abstract

The M-domain is the major regulatory subunit of cardiac myosin-binding protein-C (cMyBP-C) that modulates actin and myosin interactions to influence muscle contraction. However, the precise mechanism(s) and the specific residues involved in mediating the functional effects of the M-domain are not fully understood. Positively charged residues adjacent to phosphorylation sites in the M-domain are thought to be critical for effects of cMyBP-C on cross-bridge interactions by mediating electrostatic binding with myosin S2 and/or actin. However, recent structural studies revealed that highly conserved sequences downstream of the phosphorylation sites form a compact tri-helix bundle. Here we used site-directed mutagenesis to probe the functional significance of charged residues adjacent to the phosphorylation sites and conserved residues within the tri-helix bundle. Results confirm that charged residues adjacent to phosphorylation sites and residues within the tri-helix bundle are important for mediating effects of the M-domain on contraction. In addition, four missense variants within the tri-helix bundle that are associated with human hypertrophic cardiomyopathy caused either loss-of-function or gain-of-function effects on force. Importantly, the effects of the gain-of-function variant, L348P, increased the affinity of the M-domain for actin. Together, results demonstrate that functional effects of the M-domain are not due solely to interactions with charged residues near phosphorylatable serines and provide the first demonstration that the tri-helix bundle contributes to the functional effects of the M-domain, most likely by binding to actin.

KEYWORDS:

Cardiac Hypertrophy; Cardiac Muscle; Cardiomyopathy; Contractile Protein; Myosin-binding Protein C; Protein Phosphorylation; Tri-helix Bundle

PMID:
23782699
PMCID:
PMC3724610
DOI:
10.1074/jbc.M113.474346
[Indexed for MEDLINE]
Free PMC Article
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for HighWire Icon for PubMed Central
    Loading ...
    Support Center