Characterizations of Cross-Bridges in the Presence of Saturating Concentrations of MgAMP-PNP in Rabbit Permeabilized Psoas Muscle
Author
Frisbie, S.M.; Xu, S.; Chalovich, Joseph; Yu, L.C.
Abstract
Several earlier studies have led to different conclusions about the complex of myosin with MgAMP-PNP. It has been suggested that subfragment 1 of myosin (S1)-MgAMP-PNP forms an S1-MgADP-like state, an intermediate between the myosin S1-MgATP and myosin S1-MgADP states or a mixture of cross-bridge states. We suggest that the different states observed result from the failure to saturate S1 with MgAMP-PNP. At saturating MgAMP-PNP, the interaction of myosin S1 with actin is very similar to that which occurs in the presence of MgATP. 1) At 1°C and 170 mM ionic strength the equatorial x-ray diffraction intensity ratio I11/I10 decreased with an increasing MgAMP-PNP concentration and leveled off by ∼20 mM MgAMP-PNP. The resulting ratio was the same for MgATP-relaxed fibers. 2) The two dimensional x-ray diffraction patterns from MgATP-relaxed and MgAMP-PNP-relaxed bundles are similar. 3) The affinity of S1-MgAMP-PNP for the actin-tropomyosin-troponin complex in solution in the absence of free calcium is comparable with that of S1-MgATP. 4) In the presence of calcium, I11/I10 decreased toward the relaxed value with increasing MgAMP-PNP, signifying that the affinity between cross-bridge and actin is weakened by MgAMP-PNP. 5) The degree to which the equatorial intensity ratio decreases as the ionic strength increases is similar in MgAMP-PNP and MgATP. Therefore, results from both fiber and solution studies suggest that MgAMP-PNP acts as a non hydrolyzable MgATP analogue for myosin.
Date
1998-06
Citation:
APA:
Frisbie, S.M., & Xu, S., & Chalovich, Joseph, & Yu, L.C.. (June 1998).
Characterizations of Cross-Bridges in the Presence of Saturating Concentrations of MgAMP-PNP in Rabbit Permeabilized Psoas Muscle.
,
(),
-
. Retrieved from
http://hdl.handle.net/10342/8876
MLA:
Frisbie, S.M., and Xu, S., and Chalovich, Joseph, and Yu, L.C..
"Characterizations of Cross-Bridges in the Presence of Saturating Concentrations of MgAMP-PNP in Rabbit Permeabilized Psoas Muscle". .
. (),
June 1998.
September 27, 2023.
http://hdl.handle.net/10342/8876.
Chicago:
Frisbie, S.M. and Xu, S. and Chalovich, Joseph and Yu, L.C.,
"Characterizations of Cross-Bridges in the Presence of Saturating Concentrations of MgAMP-PNP in Rabbit Permeabilized Psoas Muscle," , no.
(June 1998),
http://hdl.handle.net/10342/8876 (accessed
September 27, 2023).
AMA:
Frisbie, S.M., Xu, S., Chalovich, Joseph, Yu, L.C..
Characterizations of Cross-Bridges in the Presence of Saturating Concentrations of MgAMP-PNP in Rabbit Permeabilized Psoas Muscle. .
June 1998;
():
.
http://hdl.handle.net/10342/8876. Accessed
September 27, 2023.
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