A conformational change in F-actin when myosin binds: fluorescence resonance energy transfer detects an increase in the radial coordinate of Cys-374.
Interactions of myosin with actin filaments probably induce conformational changes in actin which are crucial for its function. Fluorescence resonance energy transfer spectroscopy can determine changes in distance (range 10-100 A) between two probes and therefore can sense conformational changes in proteins. We have investigated changes in the radial coordinates of fluorescent probes bound to Cys-374 of F-actin when either of the isozymes (S1A1 and S1A2) of myosin subfragment 1 (S-1) bind. Using 5-[[2-[(iodoacetyl)amino]ethyl]amino]naphthalene-1-sulfonic acid and N-(4-dimethylamino-3,5-dinitrophenyl)maleimide as donor and acceptor probes, respectively, we calculated a radius of 13-14 A. This distance increased by approximately 4.5 A upon addition of S-1. No differences were detected between the effects of S1A1 and S1A2. This increase is reversed by MgATP. The average position of the probes on Cys-374 is closer to the filament axis than expected from the current models of F-actin. S-1 increases the radial position of Cys-374 either by direct interaction or via an allosteric conformational change associated with its binding.
Moens
P D
PD
Department of Anatomy and Histology, Institute for Biomedical Research, The University of Sydney, Australia. pierre@anatomy.su.oz.au
dos Remedios
C G
CG
D000199:Actins / Q000737:chemistry* / Q000378:metabolism*; D000818:Animals; D003198:Computer Simulation; D003545:Cysteine / Q000737:chemistry*; D004735:Energy Transfer; D005453:Fluorescence; D005456:Fluorescent Dyes; D008958:Models, Molecular; D009218:Myosins / Q000378:metabolism*; D009282:Naphthalenesulfonates; D011487:Protein Conformation; D011817:Rabbits; D013050:Spectrometry, Fluorescence
D000199:Actins; D005456:Fluorescent Dyes; D009282:Naphthalenesulfonates; C006421:1,5-I-AEDANS; D009218:Myosins; D003545:Cysteine