Structural differences in the crossbridge head of temperature-associated myosin subfragment-1 isoforms from carp fast skeletal muscle.
We determined the primary structures of the three acclimation-temperature-associated isoforms of myosin subfragment-1 heavy chain from fast skeletal muscle of thermally acclimated carp. These isoforms were cloned by extending 5'-regions of cDNAs that encode the rod part of myosin heavy chain specifically expressed in 10 degrees C- and 30 degrees C-acclimated carp, together with the region that encodes an intermediate structure [Imai, J., Hirayama, Y., Kikuchi, K., Kakinuma, M. & Watabe, S. (1997) J. Exp. Biol. 200, 27-34]. These three isoforms generally resembled each other in primary structure, showing 94.8, 90.9, and 92% similarity between the 10 degrees C- and intermediate-type, between the 10 degrees C- and 30 degrees C-type, and between the intermediate- and 30 degrees C-type myosin heavy chains, respectively. However, isoform-specific differences were clearly observed between the 10 degrees C- and 30 degrees C-type heavy chains in the first 60 amino acid residues from the N-terminus, where the intermediate-type showed an intermediate feature in its sequence compared to the 10 degrees C- and 30 degrees C-type isoforms. Other striking differences were observed in two surface loops between the 10 degrees C- and 30 degrees C-type isoform. Five amino acid residues out of sixteen were different in loop 1 near the ATP-binding pocket, and six out of twenty were different in loop 2 on the actin-binding site. The loops connecting beta-sheets that are known to surround the ATP-binding pocket were highly conserved in primary structure for the three types. In northern blot analysis, the accumulated mRNA levels of the 10 degrees C- and intermediate-type isoforms were significantly higher in carp acclimated to 10 degrees C and 20 degrees C than carp acclimated to 30 degrees C, whereas the level of the 30 degrees C-type isoform was significantly higher in carp acclimated to 30 degrees C than those acclimated to 10 degrees C and 20 degrees C.
Hirayama
Y
Y
Laboratory of Aquatic Molecular Biology and Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Japan.
Watabe
S
S
D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D002347:Carps; D018076:DNA, Complementary; D008969:Molecular Sequence Data; D018656:Muscle Fibers, Fast-Twitch / Q000737:chemistry*; D015879:Myosin Subfragments / Q000737:chemistry* / Q000235:genetics; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D013696:Temperature
D018076:DNA, Complementary; D015879:Myosin Subfragments; D011994:Recombinant Proteins