title: A molecular mechanism of P-loop pliability of Rho-kinase investigated by molecular dynamic simulation.
abstract: Rho-kinase is a leading player in the regulation of cytoskeletal events involving smooth muscle contraction and neurite growth-cone collapse and retraction, and is a promising drug target in the treatment of both vascular and neurological disorders. Recent crystal structure of Rho-kinase complexed with a small-molecule inhibitor fasudil has revealed structural details of the ATP-binding site, which represents the target site for the inhibitor, and showed that the conserved phenylalanine on the P-loop occupies the pocket, resulting in an increase of protein-ligand contacts. Thus, the P-loop pliability is considered to play an important role in inhibitor binding affinity and specificity. In this study, we carried out a molecular dynamic simulation for Rho-kinase-fasudil complexes with two different P-loop conformations, i.e., the extended and folded conformations, in order to understand the P-loop pliability and dynamics at atomic level. A PKA-fasudil complex was also used for comparison. In the MD simulation, the flip-flop movement of the P-loop conformation starting either from the extended or folded conformation was not able to be observed. However, a significant conformational change in a long loop region covering over the P-loop, and also alteration of ionic interaction-manner of fasudil with acidic residues in the ATP binding site were shown only in the Rho-kinase-fasudil complex with the extended P-loop conformation, while Rho-kinase with the folded P-loop conformation and PKA complexes did not show large fluctuations, suggesting that the Rho-kinase-fasudil complex with the extended P-loop conformation represents a meta-stable state. The information of the P-loop pliability at atomic level obtained in this study could provide valuable clues to designing potent and/or selective inhibitors for Rho-kinase.
authors.affiliation: Computer-Aided Molecular Modeling Research Center Kansai, Kobe, Hyogo, Japan.
authors.forename: Keigo
authors.initials: K
authors.lastname: Gohda
authors.forename: Toshio
authors.initials: T
authors.lastname: Hakoshima
mesh_terms: D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism; D003198:Computer Simulation; D017868:Cyclic AMP-Dependent Protein Kinases / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D013816:Thermodynamics; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism
chemical_list: D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D054460:rho-Associated Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; C049347:fasudil