In-cell thermodynamics and a new role for protein surfaces

There is abundant, physiologically relevant knowledge about protein cores; they are hydrophobic, exquisitely well packed, and nearly all hydrogen bonds are satisfied. An equivalent understanding of protein surfaces has remained elusive because proteins are almost exclusively studied in vitro in simp...

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Published inProceedings of the National Academy of Sciences - PNAS Vol. 113; no. 7; pp. 1725 - 1730
Main Authors Smith, Austin E., Zhou, Larry Z., Gorensek, Annelise H., Senske, Michael, Pielak, Gary J.
Format Journal Article
LanguageEnglish
Published United States National Academy of Sciences 16.02.2016
National Acad Sciences
SeriesFrom the Cover
Subjects
Animals
Drosophila
E coli
Fluorine
Hydrogen Bonding
Insects
Magnetic Resonance Spectroscopy
Physical Sciences
Protein folding
Proteins - chemistry
Signal transduction
Surface Properties
Thermodynamics
protein NMR
protein folding
in-cell NMR
protein thermodynamics
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Summary:There is abundant, physiologically relevant knowledge about protein cores; they are hydrophobic, exquisitely well packed, and nearly all hydrogen bonds are satisfied. An equivalent understanding of protein surfaces has remained elusive because proteins are almost exclusively studied in vitro in simple aqueous solutions. Here, we establish the essential physiological roles played by protein surfaces by measuring the equilibrium thermodynamics and kinetics of protein folding in the complex environment of living Escherichia coli cells, and under physiologically relevant in vitro conditions. Fluorine NMR data on the 7-kDa globular N-terminal SH3 domain of Drosophila signal transduction protein drk (SH3) show that charge–charge interactions are fundamental to protein stability and folding kinetics in cells. Our results contradict predictions from accepted theories of macromolecular crowding and show that cosolutes commonly used to mimic the cellular interior do not yield physiologically relevant information. As such, we provide the foundation for a complete picture of protein chemistry in cells.
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Edited by Martin Gruebele, University of Illinois at Urbana–Champaign, Urbana, IL, and approved December 14, 2015 (received for review September 21, 2015)
Author contributions: A.E.S. and G.J.P. designed research; A.E.S., L.Z.Z., A.H.G., and M.S. performed research; A.E.S., L.Z.Z., A.H.G., M.S., and G.J.P. analyzed data; and A.E.S., L.Z.Z., A.H.G., M.S., and G.J.P. wrote the paper.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1518620113