Abstract

Cells must balance the cost and benefit of protein expression to optimize organismal fitness. The lac operon of the bacterium Escherichia coli has been a model for quantifying the physiological impact of costly protein production and for elucidating the resulting regulatory mechanisms. We report quantitative fitness measurements in 27 redesigned operons that suggested that protein production is not the primary origin of fitness costs. Instead, we discovered that the lac permease activity, which relates linearly to cost, is the major physiological burden to the cell. These findings explain control points in the lac operon that minimize the cost of lac permease activity, not protein expression. Characterizing similar relationships in other systems will be important to map the impact of cost/benefit tradeoffs on cell physiology and regulation.

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Publisher Full Text

Authors

Eames M, Kortemme T

Institution

Graduate Group in Biophysics, MC 2530, University of California, San Francisco, CA 94158-2330, USA.

Source

Science (New York, N.Y.) 336:6083 2012 May 18 pg 911-5

MeSH

Base Sequence
Biocatalysis
Biological Transport
Escherichia coli
Escherichia coli Proteins
Gene Expression Regulation, Bacterial
Gene Knockout Techniques
Genetic Engineering
Isopropyl Thiogalactoside
Lac Operon
Lac Repressors
Lactose
Models, Biological
Molecular Sequence Data
Monosaccharide Transport Proteins
Mutation
Symporters
beta-Galactosidase

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

22605776