Spectroscopic and ITC study of the conformational change upon Ca{sup 2+}-binding in TnC C-lobe and TnI peptide complex from Akazara scallop striated muscle
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657 (Japan)
- Laboratory of Biochemistry and Biotechnology, Graduate School of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido (Japan)
Akazara scallop (Chlamys nipponensis akazara) troponin C (TnC) of striated adductor muscle binds only one Ca{sup 2+} ion at the C-terminal EF-hand motif (Site IV), but it works as the Ca{sup 2+}-dependent regulator in adductor muscle contraction. In addition, the scallop troponin (Tn) has been thought to regulate muscle contraction via activating mechanisms that involve the region spanning from the TnC C-lobe (C-lobe) binding site to the inhibitory region of the TnI, and no alternative binding of the TnI C-terminal region to TnC because of no similarity between second TnC-binding regions of vertebrate and the scallop TnIs. To clarify the Ca{sup 2+}-regulatory mechanism of muscle contraction by scallop Tn, we have analyzed the Ca{sup 2+}-binding properties of the complex of TnC C-lobe and TnI peptide, and their interaction using isothermal titration microcalorimetry, nuclear magnetic resonance, circular dichroism, and gel filtration chromatography. The results showed that single Ca{sup 2+}-binding to the Site IV leads to a structural transition not only in Site IV but also Site III through the structural network in the C-lobe of scallop TnC. We therefore assumed that the effect of Ca{sup 2+}-binding must lead to a change in the interaction mode between the C-lobe of TnC and the TnI peptide. The change should be the first event of the transmission of Ca{sup 2+} signal to TnI in Tn ternary complex.
- OSTI ID:
- 21143636
- Journal Information:
- Biochemical and Biophysical Research Communications, Vol. 369, Issue 1; Other Information: DOI: 10.1016/j.bbrc.2007.11.124; PII: S0006-291X(07)02479-5; Copyright (c) 2007 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0006-291X
- Country of Publication:
- United States
- Language:
- English
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