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Title: Insights into the Chemomechanical Coupling of the Myosin Motor from Simulation of Its ATP Hydrolysis Mechanism

Abstract

The molecular motor myosin converts chemical energy from ATP hydrolysis into mechanical work, thus driving a variety of essential motility processes. Although myosin function has been studied extensively, the catalytic mechanism of ATP hydrolysis and its chemomechanical coupling to the motor cycle are not completely understood. Here, the catalysis mechanism in myosin II is examined using quantum mechanical/molecular mechanical reaction path calculations. The resulting reaction pathways, found in the catalytically competent closed/closed conformation of the Switch-1/Switch-2 loops of myosin, are all associative with a pentavalent bipyramidal oxyphosphorane transition state but can vary in the activation mechanism of the attacking water molecule and in the way the hydrogens are transferred between the heavy atoms. The coordination bond between the Mg2+ metal cofactor and Ser237 in the Switch-1 loop is broken in the product state, thereby facilitating the opening of the Switch-1 loop after hydrolysis is completed, which is required for subsequent strong rebinding to actin. This reveals a key element of the chemomechanical coupling that underlies the motor cycle, namely, the modulation of actin unbinding or binding in response to the ATP or ADP{circle_dot}Pi state of nucleotide-bound myosin.

Authors:
 [1];  [2];  [1]
  1. University of Heidelberg
  2. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Laboratory Directed Research and Development (LDRD) Program
OSTI Identifier:
932200
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Biochemistry (American Chemical Society); Journal Volume: 45; Journal Issue: 18
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; ACTIN; ATOMS; CATALYSIS; HYDROLYSIS; MODULATION; MOTORS; MYOSIN; OPENINGS; SIMULATION; WATER

Citation Formats

Schwarzl, S.M., Smith, Jeremy C, and Fischer, S.. Insights into the Chemomechanical Coupling of the Myosin Motor from Simulation of Its ATP Hydrolysis Mechanism. United States: N. p., 2006. Web. doi:10.1021/bi052433q.
Schwarzl, S.M., Smith, Jeremy C, & Fischer, S.. Insights into the Chemomechanical Coupling of the Myosin Motor from Simulation of Its ATP Hydrolysis Mechanism. United States. doi:10.1021/bi052433q.
Schwarzl, S.M., Smith, Jeremy C, and Fischer, S.. Wed . "Insights into the Chemomechanical Coupling of the Myosin Motor from Simulation of Its ATP Hydrolysis Mechanism". United States. doi:10.1021/bi052433q.
@article{osti_932200,
title = {Insights into the Chemomechanical Coupling of the Myosin Motor from Simulation of Its ATP Hydrolysis Mechanism},
author = {Schwarzl, S.M. and Smith, Jeremy C and Fischer, S.},
abstractNote = {The molecular motor myosin converts chemical energy from ATP hydrolysis into mechanical work, thus driving a variety of essential motility processes. Although myosin function has been studied extensively, the catalytic mechanism of ATP hydrolysis and its chemomechanical coupling to the motor cycle are not completely understood. Here, the catalysis mechanism in myosin II is examined using quantum mechanical/molecular mechanical reaction path calculations. The resulting reaction pathways, found in the catalytically competent closed/closed conformation of the Switch-1/Switch-2 loops of myosin, are all associative with a pentavalent bipyramidal oxyphosphorane transition state but can vary in the activation mechanism of the attacking water molecule and in the way the hydrogens are transferred between the heavy atoms. The coordination bond between the Mg2+ metal cofactor and Ser237 in the Switch-1 loop is broken in the product state, thereby facilitating the opening of the Switch-1 loop after hydrolysis is completed, which is required for subsequent strong rebinding to actin. This reveals a key element of the chemomechanical coupling that underlies the motor cycle, namely, the modulation of actin unbinding or binding in response to the ATP or ADP{circle_dot}Pi state of nucleotide-bound myosin.},
doi = {10.1021/bi052433q},
journal = {Biochemistry (American Chemical Society)},
number = 18,
volume = 45,
place = {United States},
year = {Wed Mar 01 00:00:00 EST 2006},
month = {Wed Mar 01 00:00:00 EST 2006}
}
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