Implications of macromolecular crowding for signal transduction and metabolite channeling
Date
1998
Authors
Rohwer J.M.
Postma P.W.
Kholodenko B.N.
Westerhoff H.V.
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
The effect of different total enzyme concentrations on the flux through the bacterial phosphoenolpyruvate:carbohydrate phosphotransferase system (PTS) in vitro was determined by measuring PTS-mediated carbohydrate phosphorylation at different dilutions of cell-free extract of Escherichia coli. The dependence of the flux on the protein concentration was more than linear but less than quadratic. The combined flux-response coefficient of the four enzymes constituting the glucose PTS decreased slightly from values of ≃1.8 with increasing protein concentrations in the assay. Addition of the macromolecular crowding agents polyethylene glycol (PEG) 6000 and PEG 35000 led to a sharper decrease in the combined flux-response coefficient, in one case to values of ≃1. PEG 6000 stimulated the PTS flux at lower protein concentrations and inhibited the flux at higher protein concentrations, with the transition depending on the PEG 6000 concentration. This suggests that macromolecular crowding decreases the dissociation rate constants of enzyme complexes. High concentrations of the microsolute glycerol did not affect the combined flux-response coefficient. The data could be explained with a kinetic model of macromolecular crowding in a two-enzyme group-transfer pathway. Our results suggest that, because of the crowded environment in the cell, the different PTS enzymes form complexes that live long on the time- scale of their turnover. The implications for the metabolic behavior and control properties of the PTS, and for the effect of macromolecular crowding on nonequilibrium processes, are discussed.
Description
Keywords
carbohydrate, phosphoenolpyruvate sugar phosphotransferase, article, concentration response, dissociation constant, dna protein complex, enzyme activity, equilibrium constant, escherichia coli, macromolecule, molecular interaction, nonhuman, phosphorylation, priority journal, protein dna binding, protein dna interaction, signal transduction, Cell-Free System, Escherichia coli, Kinetics, Models, Biological, Phosphoenolpyruvate Sugar Phosphotransferase System, Signal Transduction, Bacteria (microorganisms), Escherichia coli, Negibacteria
Citation
Proceedings of the National Academy of Sciences of the United States of America
95
18
95
18