FEBS Letters | |
The kinetics of a two‐state transition of myosin subfragment 1 A temperature‐jump relaxation study | |
Lin, Shwu-Hwa2  Cheung, Herbert C.1  | |
[1] Deaprtment of Biochemistry, University of Alabama at Birmingham, UAB Station, Birmingham, AL 35294-2041, USA;Graduate Program in Biophysical Science, University of Alabama at Birmingham, UAB Station, Birmingham, AL 35294-2041, USA | |
关键词: Temperature jump; Myosin subfragment 1; SI; myosin subfragment 1; 1AF; (iodoacetamido)-fluorescien; SI-AF; SI labeled with IAF; TES; N-[tris(hydroxymethyl)methyl]-2-aminoethanesulfonic acid; εADP; 1; N o-ethenoadesine 5′-diphosphate; | |
DOI : 10.1016/0014-5793(92)80614-M | |
学科分类:生物化学/生物物理 | |
来源: John Wiley & Sons Ltd. | |
【 摘 要 】
Temperature-jump measurements were carried out on myosin subragment 1 (S1) labeled at Cys-707 with 5-(iodoacetamido)fluorescein (S1-AF). The relaxation was monitored by following the increase in the fluorescence intensity of the attached probe after a jump of 5.8°C. A single relaxation process was observed over a range of final temperatures, and the relaxation time decreased from 16.69 ms at 15°C to 3.91 ms at 27°C. The relaxation results are interpreted in terms of a two-state transition: (S1-AF)L (S1-AF)11, and the observed single relaxation time (τ) equals 1/(k + + k −). The individual first-order rate constants, k + and k −, were calculated from τ and the equilibrium constant previously determined. The activation energy was 21.9 kcal/mol for the forward reaction and 9.3 kcal/mol for the reverse reaction, corresponding to an enthalpy value of 12.6 kcal/mol for the two-state transition. The results provide, for the first time, direct kinetic evidence of a two-state transition of S1 in the absence of bound nucleotide, and support a two-state model of unliganded myosin subfragment 1.
【 授权许可】
Unknown
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