We determined
coding sequences for three types of grass carp
myosin subfragment-1 (S1)
heavy chain by extending 5'-regions of the three known genes encoding light
meromyosin isoforms (10 degrees C, intermediate and 30 degrees C types). The
primary structures of these three S1
heavy chain isoforms showed 81.4%, 81.2%, and 97.8% identities between the 10 degrees C and intermediate types, between the 10 degrees C and 30 degrees C types, and between the intermediate and 30 degrees C types, respectively. Isoform-specific differences were clearly observed between the 10 degrees C type and the other two types in 97
amino acid residues. Furthermore, among these
amino acid mutations, 51
mutations occurred at the conserved residue sites of S1
heavy chain from fish and homoiotherm. Additionally, the 10 degrees C type showed striking differences compared with the other two types in the two surface loops, loop 1 located near the ATP-binding pocket and loop 2, which is one of the actin-binding sites, suggesting that such structural differences possibly affect their motor functions. Interestingly, this 10 degrees C-type
myosin heavy chain isolated from adult grass carp
skeletal muscle was surprisingly similar to the
embryonic fast-type
myosin heavy chain from juvenile
silver carp in the structure of S1
heavy chain, indicating that it may also function as
embryonic fast-type
myosin heavy chain in juvenile stage.
