期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 284, 期 18, 页码 12318-12327出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M808850200
关键词
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资金
- National Institutes of Health [SC1HL096017, HL080367]
- National Science Foundation
- NATIONAL HEART, LUNG, AND BLOOD INSTITUTE [R01HL080367, SC1HL096017] Funding Source: NIH RePORTER
Cardiac myosin-binding protein C (cMyBP-C) is a regulatory protein expressed in cardiac sarcomeres that is known to interact with myosin, titin, and actin. cMyBP-C modulates actomyosin interactions in a phosphorylation-dependent way, but it is unclear whether interactions with myosin, titin, or actin are required for these effects. Here we show using cosedimentation binding assays, that the 4 N-terminal domains of murine cMyBP-C (i. e. C0-C1-m-C2) bind to F-actin with a dissociation constant (K-d) of similar to 10 mu M and a molar binding ratio (B-max) near 1.0, indicating 1: 1 (mol/mol) binding to actin. Electron microscopy and light scattering analyses show that these domains cross-link F-actin filaments, implying multiple sites of interaction with actin. Phosphorylation of the MyBP-C regulatory motif, or m-domain, reduced binding to actin (reduced Bmax) and eliminated actin cross-linking. These results suggest that the N terminus of cMyBP-C interacts with F-actin through multiple distinct binding sites and that binding at one or more sites is reduced by phosphorylation. Reversible interactions with actin could contribute to effects of cMyBP-C to increase crossbridge cycling.
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