J. Biol. Chem., Vol. 262, Issue 5, 1984-1988, 02, 1987
19F nuclear magnetic resonance as a probe of structural transitions and cooperative interactions in heavy meromyosin
LE Kay, JM Pascone, BD Sykes and JW Shriver
An 19F NMR probe has been attached to the reactive sulfhydryl SH1 of the
globular heads of rabbit skeletal heavy meromyosin. It serves as a
sensitive monitor of the conformational state of the heads of heavy
meromyosin in a manner similar to that seen for subfragment-1 (Shriver,
J.W., and Sykes, B.D. (1982) Biochemistry 21, 3022-3028; Tollemar, U.,
Cunningham, K., and Shriver, J.W. (1986) Biochim. Biophys. Acta 873,
243-251). The NMR spectra indicate that there are at least two states for
the heads in the SH1 region. The energetics of the interconversion of the
two states of heavy meromyosin (HMM) differs significantly from that of
S-1. In HMM in the absence of divalent cations, there are two reversible
paths between the low temperature and high temperature states with a
hysteresis-like behavior. One path is consistent with the head groups
behaving independently and similar to S-1 alone. The second path indicates
a coupling of the globular head region observed in S-1 with a second region
forming a distinctly different cooperative unit. Upon addition of Ca(II)
the hysteresis effect is lost and only the second cooperative unit is
observed. Two explanations are offered for these results: the globular
heads in HMM may couple with the S-2 segment, or the two globular heads of
HMM may couple to form a larger cooperative unit. The ability to stabilize
the larger cooperative unit with a divalent metal ion implicates a role for
the LC2 light chain in coupling regions of the myosin molecule.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
