The stability of myosin subfragment 1 (S1) to thermal denaturation has been followed by limited tryptic proteolysis. Digestions done during the thermal denaturation show that at temperatures at and above 37 degrees C there is a marked increase in the susceptibility of S1 to tryptic degradation, as evidenced by the loss of all bands corresponding to the normally trypsin-resistant fragments of 50, 27, and 21 kDa of the heavy chain and to the light chain. The enhanced digestion of S1 appears to be due to a general unfolding of all segments of S1, although the 50-kDa segment appears to unfold at a lower temperature than the remainder of the S1 structure. Digestions done after 30-min exposure to higher temperatures or after subsequent cooling to 25 degrees C show marked differences in the susceptibility of the S1 to trypsin. This suggests that, on cooling, a substantial portion of the S1, but not the 50-kDa segment, is capable of refolding to a state corresponding closely to that in the native S1. These data indicate that in terms of thermal denaturation the S1 behaves as though it is comprised of two domains--an unstable 50-kDa domain and a more stable domain comprised of the 27- and 21-kDa segments of the heavy chain interacting with the light chain, as proposed recently by Setton and Muhlrad [Setton, A., & Muhlrad, A. (1984) Arch. Biochem. Biophys. 235, 411-417]. The rates of thermal inactivation of the ATPase of S1 are found to correspond closely to the decay rates for the 50-kDa fragment, suggesting that this segment in S1 is closely associated with the ATPase function of the protein.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.