title: A Highly Conserved Yet Flexible Linker Is Part of a Polymorphic Protein-Binding Domain in Myosin-Binding Protein C.
abstract: The nuclear magnetic resonance (NMR) structure of the tri-helix bundle (THB) of the m-domain plus C2 (ΔmC2) of myosin-binding protein C (MyBP-C) has revealed a highly flexible seven-residue linker between the structured THB and C2. Bioinformatics shows significant patterns of conservation across the THB-linker sequence, with the linker containing a strictly conserved serine in all MyBP-C isoforms. Clinically linked mutations further support the functional significance of the THB-linker region. NMR, small-angle X-ray scattering, and binding studies show the THB-linker plus the first ten residues of C2 undergo dramatic changes when ΔmC2 binds Ca2+-calmodulin, with the linker and C2 N-terminal residues contributing significantly to the affinity. Modeling of all available experimental data indicates that the THB tertiary structure must be disrupted to form the complex. These results are discussed in the context of the THB-linker and the N-terminal residues of C2 forming a polymorphic binding domain that could accommodate multiple binding partners in the dynamic sarcomere.
authors.affiliation: School of Life and Environmental Sciences, The University of Sydney, NSW 2006, Australia.
authors.forename: Katharine A
authors.initials: KA
authors.lastname: Michie
authors.affiliation: School of Life and Environmental Sciences, The University of Sydney, NSW 2006, Australia.
authors.forename: Ann H
authors.initials: AH
authors.lastname: Kwan
authors.affiliation: Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, NM 87545, USA; Biology Department, University of New Mexico, Albuquerque, NM 87131, USA.
authors.forename: Chang-Shung
authors.initials: CS
authors.lastname: Tung
authors.affiliation: School of Life and Environmental Sciences, The University of Sydney, NSW 2006, Australia.
authors.forename: J Mitchell
authors.initials: JM
authors.lastname: Guss
authors.affiliation: School of Life and Environmental Sciences, The University of Sydney, NSW 2006, Australia. Electronic address: jill.trewhella@sydney.edu.au.
authors.forename: Jill
authors.initials: J
authors.lastname: Trewhella
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002147:Calmodulin / Q000378:metabolism*; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D017124:Conserved Sequence; D006801:Humans; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D011485:Protein Binding; D000072417:Protein Domains; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D053838:Scattering, Small Angle; D012694:Serine / Q000378:metabolism*; D000099163:Myosin Binding Protein C
chemical_list: D002147:Calmodulin; D002352:Carrier Proteins; D012694:Serine; D000099163:Myosin Binding Protein C
keywords: NMR; SAXS; binding domain; calmodulin; cardiac myosin binding protein C; clinically-linked mutation; distal arthrogryposis; hypertrophic cardiomyopathy; protein structure; small-angle scattering