Myosin II from rabbit skeletal muscle and Dictyostelium discoideum and its interaction with F-actin studied by (1)H NMR spectroscopy.
Mg-F-actin occurs in two conformational states, I and M, where the N-terminal amino acids are either immobile or highly mobile. In the rigor or ADP complex of rabbit myosin S1 with Mg-F-actin the N-terminal acetyl group of actin stays in its highly mobile state. The same is true for the complexes with the myosin motor domain from Dictyostelium discoideum. This excludes a direct strong interaction of the N-terminal amino acids with myosin in the rigor state as suggested. An interaction of the N-terminus of F-actin with myosin is also not promoted by occupying its low-affinity binding site(s) with divalent ions. The N-terminal high-mobility region may be part of a structural system which has evolved for releasing inadequate stress applied to the actin filaments.
Kany
Harry
H
University of Regensburg, Institute of Biophysics and Physical Biochemistry, Lehrstuhl Biologie III, Universitätsstr. 31, 93040 Regensburg, Germany.
Wolf
Jones
J
Kalbitzer
Hans Robert
HR
D000199:Actins / Q000378:metabolism*; D000205:Actomyosin / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002118:Calcium; D002413:Cations, Divalent; D004023:Dictyostelium; D008274:Magnesium; D018482:Muscle, Skeletal / Q000378:metabolism*; D024462:Myosin Type II / Q000378:metabolism*; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D011522:Protons; D011817:Rabbits; D014638:Vanadates / Q000378:metabolism
D000199:Actins; D002413:Cations, Divalent; D011522:Protons; D014638:Vanadates; D000255:Adenosine Triphosphate; D000205:Actomyosin; D024462:Myosin Type II; D008274:Magnesium; D002118:Calcium