Is SH1-SH2-Cross-Linked Myosin Subfragment 1 a Structural Analog of the Weakly-Bound State of Myosin?
Biophysical Journal, Volume 79, Issue 1, 1 July 2000, Pages 460-467 Andrey A. Bobkov and Emil Reisler Abstract Myosin subfragment 1 (S1) with SH1 (Cys707) and SH2 (Cys697) groups cross-linked by p-phenylenedimaleimide (pPDM-S1) is thought to be an analog of the weakly bound states of myosin bound to actin. The structural properties of pPDM-S1 were compared in this study to those of S1·ADP·BeFx and S1·ADP·AlF4−, i.e., the established structural analogs of the myosin weakly bound states. To distinguish between the conformational effects of SH1-SH2 cross-linking and those due to their monofunctional modification, we used S1 with the SH1 and SH2 groups labeled with N-phenylmaleimide (NPM-S1) as a control in our experiments. The state of the nucleotide pocket was probed using a hydrophobic fluorescent dye, 3-[4-(3-phenyl-2-pyrazolin-1-yl)benzene-1-sulfonylamido]phenylboronic acid (PPBA). Differential scanning calorimetry (DSC) was used to study the thermal stability of S1. By both methods t
