Conformational transitions in protein-protein association: binding of fasciculin-2 to acetylcholinesterase.
The neurotoxin fasciculin-2 (FAS2) is a picomolar inhibitor of synaptic acetylcholinesterase (AChE). The dynamics of binding between FAS2 and AChE is influenced by conformational fluctuations both before and after protein encounter. Submicrosecond molecular dynamics trajectories of apo forms of fasciculin, corresponding to different conformational substates, are reported here with reference to the conformational changes of loop I of this three-fingered toxin. This highly flexible loop exhibits an ensemble of conformations within each substate corresponding to its functions. The high energy barrier found between the two major substates leads to transitions that are slow on the timescale of the diffusional encounter of noninteracting FAS2 and AChE. The more stable of the two apo substates may not be the one observed in the complex with AChE. It seems likely that the more stable apo form binds rapidly to AChE and conformational readjustments then occur in the resulting encounter complex.
Department of Chemistry and Biochemistry, Howard Hughes Medical Institute, University of California, San Diego, La Jolla, California 92093-0365, USA. jbui@mccammon.ucsd.edu
Jennifer M
JM
Bui
Zoran
Z
Radic
Palmer
P
Taylor
J Andrew
JA
McCammon
D000110:Acetylcholinesterase / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D002800:Cholinesterase Inhibitors / Q000378:metabolism*; D003198:Computer Simulation; D004546:Elapid Venoms / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D008954:Models, Biological; D011485:Protein Binding / Q000502:physiology; D011487:Protein Conformation; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D013816:Thermodynamics
D002800:Cholinesterase Inhibitors; D004546:Elapid Venoms; C044937:fasciculin; D000110:Acetylcholinesterase