@article{5b7c1d600392496ebb8494aef16d2c4e,
title = "Cleft containing reactive thiol of myosin closes during ATP hydrolysis",
abstract = "The probe binding cleft of myosin subfragment 1 (S1) contains the reactive thiol, SH1, and tryptophan 510 (Trp-510). Solvent accessibility to Trp-510, measured using the acrylamide quenching of its fluorescence, is highest in rigor and decreases during the ATPase cycle prior to force generation. These data suggest the probe binding cleft closes during ATP hydrolysis and opens during force generation. The closing of the probe binding cleft may be the origin of the shape change of S1 during ATP hydrolysis.",
keywords = "ATPase, Bent conformation, Energy transduction, Nucleotide analog, Subfragment 1, Tryptophan",
author = "Sungjo Park and Katalin Ajtai and Burghardt, {Thomas P.}",
note = "Funding Information: where M is myosin, M * • ATP is a transient state in the cycle associated with S1 structure induced by the nucleotide analogs ATP'yS or ADPBeF x \[10,28\],a nd M* * ADP-P i is a transient state associated with S1 structure induced by the analogs ADPA1F 4 \[10\] and ADPVi \[29\]. The phosphate release step is rate limiting and associated with force generation in muscle contraction \[30\]. Our quenching data implies that the probe binding cleft is fully open without nucleotide and closes stepwise in the order given in Table 1. Comparison of scheme 2 with the quenching data (excluding ATP) shows that in the steps of the ATPase cycle preceding force generation the probe binding cleft progressively closes. This observation implies the coupling of cleft conformation and the development of force during contraction. We exclude the ATP state from consideration since two or more states of Trp-510 contribute (with different quantum efficiencies) to the apparent quenching constant complicating its interpretation \[31\], and, the distribution of intermediates in the ATP state are altered by modification of SH1 \[32\]s o that the difference of tryptophan emission from S1 and 5'-F-S1 is probably not solely Trp-5 l0 emission. The rotating cross-bridge model of contraction calls for the actin filament to be impelled by rotation of the actin bound cross-bridge. The cross-bridge transduces the chemical energy liberated by ATP hydrolysis into work by a mechanism that may involve the bending of the cross-bridge between the actin binding site at one end of S 1 and the light chain binding region at the opposite end of S1 \[33\]. The bending of S1 could be achieved by the closing and opening of the probe binding cleft containing SH1 and Trp-510 in a manner similar to that proposed earlier for the ATP binding cleft \[2\]. This work was supported by the National Institutes of Health grant R01 AR39288, the American Heart Association Grant-in-Aid 930 06610, and the Mayo Foundation.",
year = "1996",
month = aug,
day = "15",
doi = "10.1016/0167-4838(96)00086-6",
language = "English (US)",
volume = "1296",
pages = "1--4",
journal = "Biochimica et Biophysica Acta - Protein Structure and Molecular Enzymology",
issn = "0167-4838",
publisher = "Elsevier",
number = "1",
}