The local and global unfolding of coiled-coil tropomyosin.


Abstract

The thermal unfolding of a two-stranded alpha-helical coiled coil of tropomyosin was studied using circular dichroism and excimer fluorescence of N-(1-pyrenyl)iodoacetamide-labeled tropomyosin. Tropomyosin unfolds with two transitions, namely local and global unfolding at high salt (greater than 0.1 M NaCl) and pH 7.5. The local unfolding was masked by the global unfolding at low salt (less than 0.1 M NaCl), at high pH (greater than pH 9.0), and in the presence of methanol, where the global unfolding temperature was similar to or lower than the local unfolding temperature. The local and global unfolding are different in nature. A comparison of the helix thermal unfolding of N-(1-pyrenyl)iodoacetamide-tropomyosin with unlabeled tropomyosin showed that tropomyosin had an inherent less-stable region, when Cys190 was N-(1-pyrenyl)iodoacetamide-labeled, disulfide cross-linked, or reduced. Instead, the chemical state of Cys190, determined the stability of the local unfolding region, because a strain created by the disulfide cross-link or the pyrene/pyrene interaction decreases the stability of the local unfolding region. Thus, these data show that the excimer fluorescence of N-(1-pyrenyl)iodoacetamide-labeled tropomyosin is useful for studying the local and global unfolding of tropomyosin. Study holds ProTherm entries: 10063, 10064, 10065 Extra Details: additive : EDTA(1 mM),N-(1-Pyrenyl)-iodoacetamide-tropomyosin alfa-helical coli; global unfolding temperature;,local unfolding; disulfide cross-link

Submission Details

ID: 74d8u2jq3

Submitter: Connie Wang

Submission Date: April 24, 2018, 8:39 p.m.

Version: 1

Publication Details
Ishii Y,Eur. J. Biochem. (1994) The local and global unfolding of coiled-coil tropomyosin. PMID:8174550
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