AI Article Synopsis
- Temperature-jump experiments on the S-2 fragment from myosin show it can shift between alpha-helix and random coil configurations within a time frame similar to muscle crossbridge cycling.
- Two distinct relaxation times are detected—a submillisecond (tau f) and a millisecond (tau s)—following temperature increases of 5 degrees C in the 35–55 degrees C range, with maximum transitions occurring around 45 degrees C.
- The findings suggest the S-2 structure maintains significant flexibility at physiological temperatures, supporting theories like the Huxley-Simmons model regarding force generation in muscle.
Article Abstract
Temperature-jump studies on the long S-2 fragment (100,000 daltons) isolated from myosin show that this structure can undergo alpha-helix--random coil transitions in a time range approximating the cycle time of a crossbridge. Two relaxation times are observed after temperature jumps of 5 degrees C over the range 35--55 degrees C, one in the submillisecond (tau f) and the other in the millisecond (tau s) time ranges. Both processes exhibit maxima near the midpoint of the helix--coil transition (tm = 45 +/- 2 degrees C) as determined by optical rotation melt experiments. Similar results were observed for the low temperature transition (tm = 45 degrees C) of the myosin rod. Viscosity studies reveal that the S-2 particles has significant flexibility at physiological temperature. Results are considered in terms of the Huxley--Simmons and helix--coil transition models for force generation in muscle.
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|---|---|
| http://www.ncbi.nlm.nih.gov/pmc/articles/PMC383198 | PMC |
| http://dx.doi.org/10.1073/pnas.76.3.1109 | DOI Listing |
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