Thermostability of striated and smooth adductor muscle tropomyosins from Yesso scallop Mizuhopecten yessoensis

Abstract

The striated and smooth adductor muscle tropomyosins (TMs) of Yesso scallop Mizuhopecten yessoensis have been known to express different isoforms, but have not been characterized in detail to date. In the present study, TMs from both muscles of Yesso scallop were purified and their stabilities were compared by circular dichroism (CD) spectrometry and differential scanning calorimetry (DSC). From the CD data, the apparent melting temperature and the apparent free energy of folding at 20 degrees C were calculated to be 30.5 degrees C and -13.4 kJ/mol, and 36.0 degrees C and -31.9 kJ/mol for the striated and smooth muscle TMs, respectively. From the DSC data, DeltaH values were calculated to be 1.87 x 10(3) and 2.19 x 10(3) kJ/mol for striated and smooth muscle TMs. These results suggest that smooth muscle TM has higher thermostability than striated muscle TM. The amino acid residues responsible for such stability difference were considered to be the six amino acid substitutions in the middle region of the TM molecules.

Thermal Denaturation Profiles of Tuna Myoglobin

“…On the other hand, the reliability of deconvolution analysis was judged from the extinction coefficients obtained through the calculation. 19) DSC analysis. Mb was dissolved in the same medium for CD measurement.…”

“…It was suggested that thermal denaturation of tuna Mb proceeded through at least three major stages. Based on the extinction coefficients obtained through deconvolution analysis, 19) three-step denaturation of tuna Mb was considered to be more likely than the two-step denaturation. The helical content decreased as the temperature was raised (Fig.…”

Biochemical and physicochemical characteristics of the major muscle proteins from fish and shellfish

“…The positions of the amino acid substitutions among these three isoforms are characterized by a few clusters, suggesting that these isoforms are the splicing variants, but only one protein was found in the striated muscle, whereas the opaque portion of smooth muscle contains two isoforms (Ishimoda-Takagi and Kobayashi 1987). Ozawa et al (2010) isolated the major isoform, which was identified as that reported by Hasegawa (2001). The isoform in the translucent portion located between the opaque and striated muscles seems to be the same as the major isoform in the opaque portion (Ishimoda-Takagi and Kobayashi 1987).…”

“…Since the coiled-coil structure of tropomyosin unfolds by thermal treatment in a less complicated manner, the thermostability has been intensively measured for many fish species (Ochiai et al 2003(Ochiai et al , 2010aHuang et al 2004;Huang and Ochiai 2005) and also for invertebrates (Ozawa et al 2010). The decay of α-helical and coiled-coil structures can be evaluated by CD and DSC like the myosin rod.…”

Tropomyosin Isoform Expression in the Adductor Muscle of the Japanese Pearl Oyster, <i>Pinctada fucata</i>

“…TM was purified from the adductor phasic and catch muscles of P. fucata (phas- ic-TM and catch-TM, respectively) as described in a previous report [9]. The phasic adductor muscle acetone powder was extracted with 10 volumes of 20 mM Tris-HCl (pH 7.5) containing 1 M KCl and 5 mM 2-mercaptoethanol overnight, followed by centrifugation at 10,000 g for 10 min.…”