Changes in the thermal unfolding of p-phenylenedimaleimide-modified myosin subfragment 1 induced by its 'weak' binding to F-actin.
Differential scanning calorimetry (DSC) was used to analyze the thermal unfolding of myosin subfragment 1 (S1) with the SH1 (Cys-707) and SH2 (Cys-697) groups cross-linked by N,N'-p-phenylenedimaleimide (pPDM-S1). It has been shown that F-actin affects the thermal unfolding of pPDM-S1 only at very low ionic strength, when some part of pPDM-S1 binds weakly to F-actin, but not at higher ionic strength (200 mM KCl). The weak binding of pPDM-S1 to F-actin shifted the thermal transition of pPDM-S1 by about 5 degrees C to a higher temperature. This actin-induced increase in thermal stability of pPDM-S1 was similar to that observed with 'strong' binding of unmodified S1 to F-actin. Our results show that actin-induced structural changes revealed by DSC in the myosin head occur not only upon strong binding but also on weak binding of the head to F-actin, thus suggesting that these changes may occur before the power-stroke and play an important role in the motor function of the head.
Kaspieva
O V
OV
A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow, Russia.
Nikolaeva
O P
OP
Orlov
V N
VN
Ponomarev
M A
MA
Drachev
V A
VA
Levitsky
D I
DI
D000199:Actins / Q000378:metabolism*; D000818:Animals; D002152:Calorimetry, Differential Scanning; D003432:Cross-Linking Reagents; D004591:Electrophoresis, Polyacrylamide Gel; D008301:Maleimides / Q000737:chemistry* / Q000378:metabolism; D015879:Myosin Subfragments / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D017510:Protein Folding; D011817:Rabbits; D013696:Temperature
D000199:Actins; D003432:Cross-Linking Reagents; D008301:Maleimides; D015879:Myosin Subfragments; C011328:N,N'-4-phenylenedimaleimide