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How do biomolecular systems speed up and regulate rates?

REVIEW ARTICLE

Huan-Xiang Zhou

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REVIEW ARTICLE

The viability of a biological system depends upon careful regulation of the rates of various processes. These rates have limits imposed by intrinsic chemical or physical steps (e.g., diffusion). These limits can be expanded by interactions and dynamics of the biomolecules. For example, (a) a chemical reaction is catalyzed when its transition state is preferentially bound to an enzyme; (b) the folding of a protein molecule is speeded up by specific interactions within the transition-state ensemble and may be assisted by molecular chaperones; (c) the rate of specific binding of a protein molecule to a cellular target can be enhanced by mechanisms such as long-range electrostatic interactions, nonspecific binding and folding upon binding; (d) directional movement of motor proteins is generated by capturing favorable Brownian motion through intermolecular binding energy; and (e) conduction and selectivity of ions through membrane channels are controlled by interactions and the dynamics of channel proteins. Simple physical models are presented here to illustrate these processes and provide a unifying framework for understanding speed attainment and regulation in biomolecular systems.


PACS

87.15.R- Reactions and kinetics

87.17.Jj Cell locomotion, chemotaxis

87.15.Cc Folding: thermodynamics, statistical mechanics, models, and pathways

87.15.K- Molecular interactions; membrane-protein interactions

87.15.Vv Diffusion

87.16.Uv Active transport processes

Subjects

Biological physics

Dates

Issue 3 (September 2005)

Received 25 April 2005, accepted for publication 2 August 2005

Published 24 August 2005

 
Model for a F_0 motor. A sodium ion in the periplasm is driven doen the channel to the binding site by an electrochemical gradient.


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