TY - JOUR
T1 - Conformational flexibility of the Cys 697-Cys 707 segment of myosin subfragment-1. Distance distributions by frequency-domain fluorometry
AU - Cheung, Herbert C.
AU - Gryczynski, Ignacy
AU - Malak, Henryk
AU - Wiczk, Wieslaw
AU - Johnson, Michael L.
AU - Lakowicz, Joseph R.
N1 - Funding Information:
This work was supported by grants from the National Institutes of Health (AR 31239 to H.C.C. and GM 35154 to J.R.L.) and from the National Science Foundation (DMB-8804931 to J.R.L.), with support for instrumentation from the National Science Foundation (DMB-8511065) and the Center for Fluorescence Spectroscopy (DIR-8710401). J.R.L. and W.W. acknowledge support from the Medical Biotechnology Center at the University of Maryland.
PY - 1991/4
Y1 - 1991/4
N2 - The separation between Cys 697 (SH1) and Cys 707 (SH2) of the heavy chain of myosin subfragment-1 was previously measured by fluorescence resonance energy transfer with a donor linked to SH1 and an acceptor to SH2. In the present study the distribution of the distances between the two thiols was recovered from frequency-domain fluorometry. In the native state and in the presence of ligands such as MgADP, pyrophosphate, orthovanadate (Vi) and actin, we found wide distributions of the separations between SH1 and SH2 (11-16 Å) comparable to that found in the random-coil state (20 Å). These results suggest that the SH1-SH2 segment has a high degree of conformational flexibility even in native S1. The flexibility is not much affected by the physiological state of S1. However, the ligands MgADP, Vi and MgADP + Vi decrease significantly the mean SH1±SH2 distance from 27 to 17 Å with the effect of MgADP + Vi being the most pronounced. The anisotropy decay of donor-labeled S1 is biphasic with two rotational correlation times. The long component is decreased by these ligands from 289 to 93 ns, suggesting a more compact symmetric structure of S1 in the presence of the ligands. The complex S1 (MgADP)Vi has been shown to be a stable analogue of S1(MgADP)Pi, an unstable intermediate that is generated in the actomyosin ATPase cycle during muscle contraction. Since the power stroke of muscle is accompanied by release of Pi from S1(MgADP)Pi, the present results are consistent with a model in which force generation can be accompanied by transition of S1 from a highly symmetric or compact structure to a more extended structure.
AB - The separation between Cys 697 (SH1) and Cys 707 (SH2) of the heavy chain of myosin subfragment-1 was previously measured by fluorescence resonance energy transfer with a donor linked to SH1 and an acceptor to SH2. In the present study the distribution of the distances between the two thiols was recovered from frequency-domain fluorometry. In the native state and in the presence of ligands such as MgADP, pyrophosphate, orthovanadate (Vi) and actin, we found wide distributions of the separations between SH1 and SH2 (11-16 Å) comparable to that found in the random-coil state (20 Å). These results suggest that the SH1-SH2 segment has a high degree of conformational flexibility even in native S1. The flexibility is not much affected by the physiological state of S1. However, the ligands MgADP, Vi and MgADP + Vi decrease significantly the mean SH1±SH2 distance from 27 to 17 Å with the effect of MgADP + Vi being the most pronounced. The anisotropy decay of donor-labeled S1 is biphasic with two rotational correlation times. The long component is decreased by these ligands from 289 to 93 ns, suggesting a more compact symmetric structure of S1 in the presence of the ligands. The complex S1 (MgADP)Vi has been shown to be a stable analogue of S1(MgADP)Pi, an unstable intermediate that is generated in the actomyosin ATPase cycle during muscle contraction. Since the power stroke of muscle is accompanied by release of Pi from S1(MgADP)Pi, the present results are consistent with a model in which force generation can be accompanied by transition of S1 from a highly symmetric or compact structure to a more extended structure.
KW - Anisotropy decay
KW - Distance distribution
KW - Frequency-domain fluorometry
KW - Myosin subfragment-1
UR - http://www.scopus.com/inward/record.url?scp=0025726760&partnerID=8YFLogxK
U2 - 10.1016/0301-4622(91)85025-L
DO - 10.1016/0301-4622(91)85025-L
M3 - Article
C2 - 1873469
AN - SCOPUS:0025726760
SN - 0301-4622
VL - 40
SP - 1
EP - 17
JO - Biophysical Chemistry
JF - Biophysical Chemistry
IS - 1
ER -