The rate constant of modification of a specific thiol group, SH2, with N-ethylmaleimide (NEM) has been used to estimate the conformational change in the local area containing SH2 (SH2 region) of skeletal myosin as a structural probe. The rate of Mg2+-ATP-induced SH2 modification of subfragment-1 (S-l) isozymes was regulated by Ca2+ in the pCa range below 6.4 and was not regulated in the pCa range above 6.4. No substantial difference between S-1 containing alkali light chain, A1, (S-1(A1)) and S-1 containing alkali light chain, A2, (S-1(A2)) was observed in the Ca2+-dependent rate of SH2 modification. Due to the presence of this Ca2+ regulation in myosin (absence in S-1 isozymes) in the pCa range above 6.4, absence of 5,5′-dithiobis-(2-nitrobenzoic acid) (DTNB) light chain in S-1 isozymes, and high affinity of Ca2+ for DTNB light chain, this Ca2+ regulation in the pCa range above 6.4 is possibly related to the Ca2+ binding to DTNB light chain. F-Actin, which is entirely free from tropomyosin and troponin, enhanced the rate of Mg2+-ATP-induced SH2 modification of S-1 isozymes equally and of myosin, and reduced the Ca2+ sensitivity with an increase in F-actin concentration.
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July 01 1987
Effect of calcium and F-actin on the rate of SH2 modification in skeletal myosin Available to Purchase
Tsuneo Kameyama;
Tsuneo Kameyama
1Department of Biochemistry, School of Medicine, Juntendo University, Hongo-2, Bunkyo-ku, Tokyo 113, Japan
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Mitsuko K. Ishii;
Mitsuko K. Ishii
1Department of Biochemistry, School of Medicine, Juntendo University, Hongo-2, Bunkyo-ku, Tokyo 113, Japan
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Takashi Yoshiike
Takashi Yoshiike
2Department of Dermatology, School of Medicine, Juntendo University, Hongo-2, Bunkyo-ku, Tokyo 113, Japan
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Publisher: Portland Press Ltd
Received:
June 15 1987
Online ISSN: 1573-4935
Print ISSN: 0144-8463
© 1987 Plenum Publishing Corporation
1987
Biosci Rep (1987) 7 (7): 543–551.
Article history
Received:
June 15 1987
Citation
Tsuneo Kameyama, Mitsuko K. Ishii, Takashi Yoshiike; Effect of calcium and F-actin on the rate of SH2 modification in skeletal myosin. Biosci Rep 1 July 1987; 7 (7): 543–551. doi: https://doi.org/10.1007/BF01119770
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