title: Facilitated cross-bridge interactions with thin filaments by familial hypertrophic cardiomyopathy mutations in α-tropomyosin.
abstract: Familial hypertrophic cardiomyopathy (FHC) is a disease of cardiac sarcomeres. To identify molecular mechanisms underlying FHC pathology, functional and structural differences in three FHC-related mutations in recombinant α-Tm (V95A, D175N, and E180G) were characterized using both conventional and modified in vitro motility assays and circular dichroism spectroscopy. Mutant Tm's exhibited reduced α-helical structure and increased unordered structure. When thin filaments were fully occupied by regulatory proteins, little or no motion was detected at pCa 9, and maximum speed (pCa 5) was similar for all tropomyosins. Ca(2+)-responsiveness of filament sliding speed was increased either by increased pCa(50) (V95A), reduced cooperativity n (D175N), or both (E180G). When temperature was increased, thin filaments with E180G exhibited dysregulation at temperatures ~10°C lower, and much closer to body temperature, than WT. When HMM density was reduced, thin filaments with D175N required fewer motors to initiate sliding or achieve maximum sliding speed.
authors.affiliation: Department of Biological Science, The Florida State University, Tallahassee, FL 32306-4295, USA.
authors.forename: Fang
authors.initials: F
authors.lastname: Wang
authors.forename: Nicolas M
authors.initials: NM
authors.lastname: Brunet
authors.forename: Justin R
authors.initials: JR
authors.lastname: Grubich
authors.forename: Ewa A
authors.initials: EA
authors.lastname: Bienkiewicz
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Asbury
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Compton
authors.forename: Goran
authors.initials: G
authors.lastname: Mihajlović
authors.forename: Victor F
authors.initials: VF
authors.lastname: Miller
authors.forename: P Bryant
authors.initials: PB
authors.lastname: Chase
mesh_terms: D000199:Actins / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D024741:Cardiomyopathy, Hypertrophic, Familial / Q000235:genetics* / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D008297:Male; D009154:Mutation; D015879:Myosin Subfragments / Q000737:chemistry / Q000378:metabolism; D011817:Rabbits; D013696:Temperature; D014335:Tropomyosin / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*
chemical_list: D000199:Actins; D015879:Myosin Subfragments; D014335:Tropomyosin; D002118:Calcium