ATP-induced structural change in myosin subfragment-1 revealed by the location of protease cleavage sites on the primary structure.
To understand the nature of the ATP-induced structural change in myosin subfragment-1, rabbit and chicken skeletal subfragments-1s were cleaved by various proteolytic enzymes in the absence, and in the presence, of ATP and the exact locations of the cleavage sites that were affected by ATP were determined from the amino end analysis of fragments by the use of a protein sequencer. It was found that subtilisin cleaved a site between Gln27 and Asn28 of rabbit subfragment-1 and between Gln28 and Asn29 of chicken subfragment-1 only in the presence of ATP. Thermolysin cleaved a site between Pro31 and Phe32 of chicken subfragment-1 in the presence of ATP, but the same site of rabbit subfragment-1 was not cleaved. The location of these sites is quite similar to the ATP-induced chymotryptic cleavage site of chicken gizzard heavy meromyosin, between Trp29 and Ser30 as reported by others. It is suggested, therefore, that the structure and the ATP-induced structural change in the regions are similar in these subfragment-1s. ATP also changes the cleavage rate of the 26K-50K junction by many proteases. Exact cleavage sites were determined and the relationship between their location and the suppression or the enhancement by ATP of the cleavage was studied. It was found that the cleavage sites were restricted to a quite narrow region and only the cleavage by thermolysin that attacked the middle of the region was enhanced by ATP. The distribution of the cleavage sites and the effect of ATP suggest that ATP induces drastic structural change at the middle of the 26K-50K junction region. The region attacked easily by many proteases coincided very well with a hydrophilic region indicated by the hydropathy index. The region probably protrudes outside and is, therefore, easily attacked by many proteases.
Yamamoto
K
K
Faculty of Liberal Arts, University of the Air, Chiba, Japan.
D000255:Adenosine Triphosphate / Q000502:physiology*; D000595:Amino Acid Sequence; D000818:Animals; D002850:Chromatography, Gel; D008970:Molecular Weight; D009119:Muscle Contraction; D015879:Myosin Subfragments / Q000032:analysis / Q000378:metabolism*; D010446:Peptide Fragments; D011487:Protein Conformation; D013045:Species Specificity
D015879:Myosin Subfragments; D010446:Peptide Fragments; D000255:Adenosine Triphosphate