期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1982
卷号：79
期号：4
页码：958-962
DOI：10.1073/pnas.79.4.958
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：One of the products of the limited tryptic hydrolysis of chymotryptic myosin subfragment 1 is the 27,000-dalton NH2-terminal fragment. This fragment is generated by two parallel routes from either the 75,000- or 95,000-dalton peptide of the heavy chain: (i) through a 20,500-dalton precursor or (ii) directly without participation of a precursor. Lowering of pH and temperature and increasing of ionic strength inhibited route i digestion in comparison to route ii. MgATP and its derivatives in millimolar concentration substantially suppressed route i digestion. Suppression of route i digestion depended on the concentration of MgATP. It occurred after a lag phase when the ratio of MgATP to subfragment 1 concentrations was greater than 0.5. In contrast, the MgATP-induced increase in tryptophan fluorescence of myosin subfragment 1 appeared without a lag phase. The generation of the 27,000-dalton fragment by either route was not affected by F-actin however, the suppression of route i digestion induced by MgADP was abolished when myosin subfragment 1 was in ternary complex with actin and MgADP. We conclude that the 27,000/50,000-dalton hinge region is a flexible domain of the myosin head and that conformation of this region is sensitive to the presence of nucleotides and actin and to variations in ambient factors.
