{
    "abstract": "We investigated how strong cross-bridge number affects sliding speed of regulated Ca(2+)-activated, thin filaments. First, using in vitro motility assays, sliding speed decreased nonlinearly with reduced density of heavy meromyosin (HMM) for regulated (and unregulated) F-actin at maximal Ca(2+). Second, we varied the number of Ca(2+)-activatable troponin complexes at maximal Ca(2+) using mixtures of recombinant rabbit skeletal troponin (WT sTn) and sTn containing sTnC(D27A,D63A), a mutant deficient in Ca(2+) binding at both N-terminal, low affinity Ca(2+)-binding sites (xxsTnC-sTn). Sliding speed decreased nonlinearly as the proportion of WT sTn decreased. Speed of regulated thin filaments varied with pCa when filaments contained WT sTn but filaments containing only xxsTnC-sTn did not move. pCa(50) decreased by 0.12-0.18 when either heavy meromyosin density was reduced to approximately 60% or the fraction of Ca(2+)-activatable regulatory units was reduced to approximately 33%. Third, we exchanged mixtures of sTnC and xxsTnC into single, permeabilized fibers from rabbit psoas. As the proportion of xxsTnC increased, unloaded shortening velocity decreased nonlinearly at maximal Ca(2+). These data are consistent with unloaded filament sliding speed being limited by the number of cycling cross-bridges so that maximal speed is attained with a critical, low level of actomyosin interactions.",
    "authors": [
        {
            "affiliation": "Department of Physiology and Biophysics, University of Washington, Seattle, Washington 98195, USA.",
            "firstname": "Bo",
            "initials": "B",
            "lastname": "Liang"
        },
        {
            "affiliation": null,
            "firstname": "Ying",
            "initials": "Y",
            "lastname": "Chen"
        },
        {
            "affiliation": null,
            "firstname": "Chien-Kao",
            "initials": "CK",
            "lastname": "Wang"
        },
        {
            "affiliation": null,
            "firstname": "Zhaoxiong",
            "initials": "Z",
            "lastname": "Luo"
        },
        {
            "affiliation": null,
            "firstname": "Michael",
            "initials": "M",
            "lastname": "Regnier"
        },
        {
            "affiliation": null,
            "firstname": "Albert M",
            "initials": "AM",
            "lastname": "Gordon"
        },
        {
            "affiliation": null,
            "firstname": "P Bryant",
            "initials": "PB",
            "lastname": "Chase"
        }
    ],
    "conclusions": null,
    "copyrights": null,
    "doi": "10.1016/S0006-3495(03)74607-4",
    "journal": "Biophysical journal",
    "keywords": [],
    "methods": null,
    "publication_date": "2003-08-29",
    "pubmed_id": "12944292\n10900175\n9245729\n6824759\n10545369\n9148936\n8662810\n2944885\n10837336\n9512039\n2969265\n7858136\n8487194\n314510\n7713874\n9889829\n10747208\n9138575\n8325853\n8785348\n10747195\n1550212\n8246794\n7948690\n8785301\n12759477\n2034132\n11892277\n12944292\n8675696\n6214692\n7858135\n2455798\n11262388\n3795099\n3723106\n7121269\n7121270\n2745448\n8913615\n9545059\n11956338\n10233080\n8246800\n6289041\n10692331\n9826713\n8626536\n2143785\n9679172",
    "results": null,
    "title": "Ca2+ regulation of rabbit skeletal muscle thin filament sliding: role of cross-bridge number.",
    "xml": "<Element 'PubmedArticle' at 0x788505be9210>"
}