TY - JOUR
T1 - The rate of MgADP binding to and dissociation from acto-S1
AU - Borejdo, J.
AU - Ando, T.
AU - Burghardt, T. P.
N1 - Funding Information:
We thank Ms. Carroll Flynn for excellent technical assistance and Professor M. Morales for support and Professor Roger Cooke for EPR measure- ments. This research was supported by grants HL-16683 from USPHS, PCM-7922174 from NSF and by a grant from Muscular Dystrophy Association. J.B. is an Established Investigator and T.P.B. is a postdoctoral fellow of the American Heart Association.
PY - 1985/4/5
Y1 - 1985/4/5
N2 - The rate of binding and dissociation of MgADP from its ternary complex with actin and S1 was measured by following the extent to which fixed concentrations of MgADP slow down MgATP-induced dissociation of acto-S1. The solution of the equations describing this process shows that at any MgADP concentration the apparent rate of acto-S1 dissociation should be proportional to a square root of the equilibrium constant for MgADP dissociation and to MgATP concentration. By measuring the apparent rate of acto-S1 dissociation as a function of MgATP concentration, the rate of MgADP binding and dissociation were determined as 5 · 106 M-1 · s-1 and 1400 s-1, respectively. These rates were unchanged by modification of SH1 thiol of S1 by a variety of fluorescence and spin-labels, but dissociation rate was drastically reduced when SH1 was labelled with 5-iodoacetamidofluorescein.
AB - The rate of binding and dissociation of MgADP from its ternary complex with actin and S1 was measured by following the extent to which fixed concentrations of MgADP slow down MgATP-induced dissociation of acto-S1. The solution of the equations describing this process shows that at any MgADP concentration the apparent rate of acto-S1 dissociation should be proportional to a square root of the equilibrium constant for MgADP dissociation and to MgATP concentration. By measuring the apparent rate of acto-S1 dissociation as a function of MgATP concentration, the rate of MgADP binding and dissociation were determined as 5 · 106 M-1 · s-1 and 1400 s-1, respectively. These rates were unchanged by modification of SH1 thiol of S1 by a variety of fluorescence and spin-labels, but dissociation rate was drastically reduced when SH1 was labelled with 5-iodoacetamidofluorescein.
KW - (Rabbit skeletal muscle)
KW - Actin-myosin interaction
KW - Dissociation rate constant
KW - Fluorescence probe
KW - MgADP binding
KW - Myosin subfragment 1
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U2 - 10.1016/0167-4838(85)90054-8
DO - 10.1016/0167-4838(85)90054-8
M3 - Article
C2 - 3872135
AN - SCOPUS:0021917111
SN - 0167-4838
VL - 828
SP - 172
EP - 176
JO - Biochimica et Biophysica Acta (BBA)/Protein Structure and Molecular
JF - Biochimica et Biophysica Acta (BBA)/Protein Structure and Molecular
IS - 2
ER -