1zac
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N-DOMAIN OF TROPONIN C FROM CHICKEN SKELETAL MUSCLE, NMR, MINIMIZED AVERAGE STRUCTURE
OverviewOverview
Contractile activity of skeletal muscle is triggered by a Ca2+-induced, "opening" of the regulatory N-domain of troponin C (apo-NTnC residues, 1-90). This structural transition has become a paradigm for large-scale, conformational changes that affect the interaction between proteins. The, regulatory domain is comprised of two basic structural elements: one, contributed by the N-, A-, and D-helices (NAD unit) and the other by the, B- and C-helices (BC unit). The Ca2+-induced opening is characterized by a, movement of the BC unit away from the NAD unit with a concomitant change, in conformation at two hinges (Glu41 and Val65) of the BC unit. To examine, the effect of low temperatures on this Ca2+-induced structural change and, the implications for contractile regulation, we have examined nuclear, magnetic resonance (NMR) spectral changes of apo-NTnC upon decreasing the, temperature from 30 to 4 degrees C. In addition, we have determined the, solution structure of apo-NTnC at 4 degrees C using multinuclear, multidimensional NMR spectroscopy. Decreasing temperatures induce a, decrease in the rates and amplitudes of pico to nanosecond time scale, backbone dynamics and an increase in alpha-helical content for the, terminal helices of apo-NTnC. In addition, chemical shift changes for the, Halpha resonances of Val65 and Asp66, the hinge residues of the BC, unit, were observed. Compared to the solution structure of apo-NTnC determined, at 30 degrees C, the BC unit packs more tightly against the NAD unit in, the solution structure determined at 4 degrees C. Concomitant with the, tighter packing of the BC and NAD structural units, a decrease in the, total exposed hydrophobic surface area is observed. The results have broad, implications relative to structure determination of proteins in the, presence of large domain movements, and help to elucidate the relevance of, structures determined under different conditions of physical state and, temperature, reflecting forces ranging from crystal packing to solution, dynamics.
About this StructureAbout this Structure
1ZAC is a Single protein structure of sequence from Gallus gallus. Known structural/functional Sites: and . Full crystallographic information is available from OCA.
ReferenceReference
Low-temperature-induced structural changes in the Apo regulatory domain of skeletal muscle troponin C., Tsuda S, Miura A, Gagne SM, Spyracopoulos L, Sykes BD, Biochemistry. 1999 May 4;38(18):5693-700. PMID:10231519
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