Functional and spectroscopic studies of an familial hypertrophic cardiomyopathy mutation in Motif X of cardiac myosin binding protein-C

Louise J. Brown, Leena Singh, Kenneth L. Sale, Bing Yu, Ronald Trent, Peter G. Fajer, Brett D. Hambly*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)

Abstract

Familial hypertrophic cardiomyopathy is an autosomal dominant genetic disorder caused by mutations in cardiac sarcomeric proteins. One such mutation is a six amino acid duplication of residues 1248–1253 in the C-terminal immunoglobulin domain of cardiac myosin binding protein-C, referred to as Motif X. Motif X binds the myosin rod and titin. Here we investigate the structural and functional alteration in the mutant Motif X protein to understand how sarcomeric dysfunction may occur. The cDNA encoding Motif X was cloned, mutated and expressed as wild-type and mutant proteins in a bacterial expression system. Circular dichroism spectroscopy confirmed that the normal and mutant Motif X exhibited a high β-content, as predicted for immunoglobulin domains. Thermal denaturation curves showed that Motif X unfolded with at least two structural transitions, with the first transition occurring at 63 °C in the wild-type but at 40 °C in the mutant, consistent with the mutant being structurally less stable. Sedimentation binding studies with synthetic myosin filaments revealed no significant difference in binding to myosin between the wild-type and the mutant Motif X. Molecular modeling of this duplication mutation onto an homologous IgI structure (telokin) revealed that the duplicated residues lie within the F strand of the immunoglobulin fold, on a surface of Motif X distant from residues previously implicated in myosin binding. Taken together, these data suggest that the Motif X mutation may interfere with other, as yet unidentified, functional interactions.
Original languageEnglish
Pages (from-to)400-408
Number of pages9
JournalEuropean Biophysics Journal
Volume31
Issue number5
DOIs
Publication statusPublished - Aug 2002
Externally publishedYes

Keywords

  • myosin binding protein-C
  • familial hypertrophic cardiomyopathy
  • cardiac muscle

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