| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2002: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2001: ¥2,200,000 (Direct Cost: ¥2,200,000)
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| Research Abstract |
The relationship between thermodynamic properties and isoform composition of tropomyosin (TM) in fish ordinary (fast) and dark (slow) muscles were investigated. Ordinary muscle TM showed one to two endothermic peaks in differential scanning calorimetry (DSC) analysis, while dark muscle counterpart showed four to five peaks. The numbers of peaks seemed to correspond to those of isoforms as checked by two-dimensional gel electrophoresis. In the next place, cDNAs encoding TM were cloned from the ordinary muscle of white croaker, walleye pollack and bluefin tuna, and the nucleotide sequences were analyzed and the amino acid sequences were deduced, except for tuna β-chain. It was revealed that the heptad repeat structure stabilizing the coiled-coil structure of TM, about ten residues each of N- and C-termini, and Cys190 were conserved among fish TMs so far sequenced. Transient temperature (Tm) in DSC ranged from 38.4 - 48.9℃, suggesting that thermostabilities of fish TMs are clearly different from each other. Temperature dependency of CD spectra suggested that the major structural change through thermal denaturation of TM is the decay of α-helices. Refolding after heating and cooling was almost complete in the case of white croaker and walleye pollack TMs, but was rather incomplete in the case of bluefin tuna TM. It was suggested that species-specific stability difference of TM was considered to be due to those residues on molecular surface. On the other hand, the properties of another regulatory protein, α-actinin were partially investigated.
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