RGD Reference Report - Regulation of force and unloaded sliding speed in single thin filaments: effects of regulatory proteins and calcium. - Rat Genome Database

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Regulation of force and unloaded sliding speed in single thin filaments: effects of regulatory proteins and calcium.

Authors: Homsher, E  Lee, DM  Morris, C  Pavlov, D  Tobacman, LS 
Citation: Homsher E, etal., J Physiol. 2000 Apr 1;524 Pt 1:233-43.
RGD ID: 8554013
Pubmed: PMID:10747195   (View Abstract at PubMed)
PMCID: PMC2269863   (View Article at PubMed Central)

1. Measurements of the unloaded sliding speed of and isometric force exerted on single thin filaments in in vitro motility assays were made to evaluate the role of regulatory proteins in the control of unloaded thin filament sliding speed and isometric force production. 2. Regulated actin filaments were reconstituted from rabbit F-actin, native bovine cardiac tropomyosin (nTm), and either native bovine cardiac troponin (nTn), troponin containing a TnC mutant, CBMII, in which the sole regulatory site in cardiac TnC (site II) is inactivated (CBMII-Tn), or troponin containing a point mutation in TnT (I79N, where isoleucine at position 79 is replaced with asparagine) associated with familial hypertrophic cardiomyopathy (FHC). 3. Addition of regulatory proteins to the thin filament increases both the unloaded sliding speed and the isometric force exerted by myosin heads on the thin filaments. 4. Variation of thin filament activation by varying [Ca2+] or the fraction of CBMII/TnC bound to the thin filament at pCa 5, had little effect on the unloaded filament sliding speed until the fraction of the thin filament containing calcium bound to TnC was less than 0.15. These results suggest that [Ca2+] primarily affects the number of attached and cycling crossbridges. 5. The presence of the FHC TnT mutant increased the thin filament sliding speed but reduced the isometric force that heavy meromyosin exerted on regulated thin filaments. These latter results, together with the increased sliding speed and isometric force seen in the presence of regulatory proteins, suggest that thin filament regulatory proteins exert significant allosteric effects on the interaction of crossbridges with the thin filament.



Gene Ontology Annotations    Click to see Annotation Detail View

Biological Process

  
Object SymbolSpeciesTermQualifierEvidenceWithNotesSourceOriginal Reference(s)
Tnnt2Ratregulation of muscle filament sliding speed involved_inIMP PMID:10747195BHF-UCL 

Objects Annotated

Genes (Rattus norvegicus)
Tnnt2  (troponin T2, cardiac type)


Additional Information