The Primary Structure of Skeletal Muscle Myosin Heavy Chain: III. Sequence of the 22 kDa Fragment and the Alignment of the 23 kDa, 50 kDa, and 22 kDa Fragments

The amino acid sequence of the 197-residue 22 kDa fragment from chicken pectoralis muscle was determined to be as follows: K-K-G-S-S-F-Q-T-V-S-A-L-F-R-E-N-L-N-K-L-M-A-N-L-R-S-T-H-P-H-F-V-R-C-I-I-P-N-E-T-K-T-P-G-A-M-E-H-E-L-V-L-H-Q-L-R-C-N-G-V-L-E-G-I-R-I-C-R-K-G-F-P-S-R-V-L-Y-A-D-F-K-Q-R-Y-R-V-L-N-A-S-A-I-P-E-G-Q-F-M-D-S-K-K-A-S-E-K-L-L-G-S-I-D-V-D-h-T-Q-Y-R-F-G-H-T-K-V-F-F-K-A-G-L-L-G-L-L-E-E-M-R-D-D-K-L-A-E-I-I-T-R-T-Q-A-R-C-R-G-F-L-M-R-V-E-Y-R-R-M-V-E-R-R-E-S-I-F-C-I-Q-Y-N-V-R-S-F-M-N-V-K-H-W-P-W-M-K-L-F-F-K, where h stands for 3-N-methylhistidine. The amino acid sequences of the 22 kDa fragment and its equivalent fragment from chicken ventricle and gizzard muscle myosins were also determined by our group. Predicted secondary structures of these 22 kDa fragment regions and of the reported chicken embryo myosin revealed some possible structural differences. There is a highly conserved 15-residue region in the vicinity of reactive cysteine residues, a region which has been suggested to bind actin and ATP analogue. This possible functional region may have a unique secondary structure containing a turn or coil structure.