title: Dynamics of tropomyosin in muscle fibers as monitored by saturation transfer EPR of bi-functional probe.
abstract: The dynamics of four regions of tropomyosin was assessed using saturation transfer electron paramagnetic resonance in the muscle fiber. In order to fully immobilize the spin probe on the surface of tropomyosin, a bi-functional spin label was attached to i,i+4 positions via cysteine mutagenesis. The dynamics of bi-functionally labeled tropomyosin mutants decreased by three orders of magnitude when reconstituted into "ghost muscle fibers". The rates of motion varied along the length of tropomyosin with the C-terminus position 268/272 being one order of magnitude slower then N-terminal domain or the center of the molecule. Introduction of troponin decreases the dynamics of all four sites in the muscle fiber, but there was no significant effect upon addition of calcium or myosin subfragment-1.
authors.affiliation: Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida, United States of America.
authors.forename: Roni F
authors.initials: RF
authors.lastname: Rayes
authors.forename: Tamás
authors.initials: T
authors.lastname: Kálai
authors.forename: Kálmán
authors.initials: K
authors.lastname: Hideg
authors.forename: Michael A
authors.initials: MA
authors.lastname: Geeves
authors.forename: Piotr G
authors.initials: PG
authors.lastname: Fajer
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D002942:Circular Dichroism; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D013058:Mass Spectrometry; D018485:Muscle Fibers, Skeletal / Q000378:metabolism*; D009218:Myosins / Q000378:metabolism; D011817:Rabbits; D044366:Transition Temperature; D014335:Tropomyosin / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D000199:Actins; D014335:Tropomyosin; D009218:Myosins