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Unfolding domains of recombinant fusion αα‐tropomyosin
Author(s) -
Ishii Yoshiharu,
HitchcockDegregori Sarah,
Mabuchi Katsuhide,
Lehrer Sherwin S.
Publication year - 1992
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1002/pro.5560011011
Subject(s) - tropomyosin , recombinant dna , computational biology , fusion , fusion protein , chemistry , biophysics , biology , biochemistry , actin , philosophy , gene , linguistics
The thermal unfolding of the coiled‐coil α ‐helix of recombinant αα ‐tropomyosin from rat striated muscle containing an additional 80‐residue peptide of influenza virus NS1 protein at the N‐terminus (fusion‐tropomyosin) was studied with circular dichroism and fluorescence techniques. Fusion‐tropomyosin unfolded in four cooperative transitions: (1) a pretransition starting at 35 °C involving the middle of the molecule; (2) a major transition at 46 °C involving no more than 36% of the helix from the C‐terminus; (3) a major transition at 56 °C involving about 46% of the helix from the N‐terminus; and (4) a transition from the nonhelical fusion domain at about 70 °C. Rabbit skeletal muscle tropomyosin, which lacks the fusion peptide but has the same tropomyosin sequence, does not exhibit the 56 °C or 70 °C transition. The very stable fusion unfolding domain of fusion‐tropomyosin, which appears in electron micrographs as a globular structural domain at one end of the tropomyosin rod, acts as a crosslink to stabilize the adjacent N‐terminal domain. The least stable middle of the molecule, when unfolded, acts as a boundary to allow the independent unfolding of the C‐terminal domain at 46 °C from the stabilized N‐terminal unfolding domain at 56 °C. Thus, strong localized interchain interactions in coiled‐coil molecules can increase the stability of neighboring domains.