Reversible movement of switch 1 loop of myosin determines actin interaction.
The conserved switch 1 loop of P-loop NTPases is implicated as a central element that transmits information between the nucleotide-binding pocket and the binding site of the partner proteins. Recent structural studies have identified two states of switch 1 in G-proteins and myosin, but their role in the transduction mechanism has yet to be clarified. Single tryptophan residues were introduced into the switch 1 region of myosin II motor domain and studied by rapid reaction methods. We found that in the presence of MgADP, two states of switch 1 exist in dynamic equilibrium. Actin binding shifts the equilibrium towards one of the MgADP states, whereas ATP strongly favors the other. In the light of electron cryo-microscopic and X-ray crystallographic results, these findings lead to a specific structural model in which the equilibrium constant between the two states of switch 1 is coupled to the strength of the actin-myosin interaction. This has implications for the enzymatic mechanism of G-proteins and possibly P-loop NTPases in general.
Kintses
Bálint
B
Department of Biochemistry, Eötvös Lorand University, Budapest, Hungary.
Gyimesi
Máté
M
Pearson
David S
DS
Geeves
Michael A
MA
Zeng
Wei
W
Bagshaw
Clive R
CR
Málnási-Csizmadia
András
A
D000199:Actins / Q000737:chemistry*; D000244:Adenosine Diphosphate / Q000737:chemistry; D000255:Adenosine Triphosphate / Q000737:chemistry; D000818:Animals; D020285:Cryoelectron Microscopy; D018360:Crystallography, X-Ray; D004023:Dictyostelium; D008274:Magnesium / Q000737:chemistry; D008956:Models, Chemical; D008958:Models, Molecular; D009218:Myosins / Q000737:chemistry*; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D014364:Tryptophan / Q000737:chemistry
D000199:Actins; D000244:Adenosine Diphosphate; D014364:Tryptophan; D000255:Adenosine Triphosphate; D009218:Myosins; D008274:Magnesium