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Probing gene expression in live cells, one protein molecule at a time.

We directly observed real-time production of single protein molecules in individual Escherichia coli cells. A fusion protein of a fast-maturing yellow fluorescent protein (YFP) and a membrane-targeting peptide was expressed under a repressed condition. The membrane-localized YFP can be detected with single-molecule sensitivity. We found that the protein molecules are produced in bursts, with each burst originating from a stochastically transcribed single messenger RNA molecule, and that protein copy numbers in the bursts follow a geometric distribution. The quantitative study of low-level gene expression demonstrates the potential of single-molecule experiments in elucidating the workings of fundamental biological processes in living cells.

Pubmed ID: 16543458


  • Yu J
  • Xiao J
  • Ren X
  • Lao K
  • Xie XS


Science (New York, N.Y.)

Publication Data

March 17, 2006

Associated Grants


Mesh Terms

  • Bacterial Proteins
  • Blotting, Western
  • Escherichia coli K12
  • Escherichia coli Proteins
  • Fluorescence
  • Gene Expression
  • Gene Expression Profiling
  • Luminescent Proteins
  • Membrane Proteins
  • Microscopy, Fluorescence
  • Molecular Probe Techniques
  • Poisson Distribution
  • Promoter Regions, Genetic
  • RNA, Bacterial
  • RNA, Messenger
  • Recombinant Fusion Proteins
  • Reverse Transcriptase Polymerase Chain Reaction
  • Stochastic Processes