期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：6
页码：1739-1742
DOI：10.1073/pnas.1417415112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceGlobular proteins perform many of the chemical reactions required for life. The prevailing model of globular protein structure, which is based on studies in dilute solutions, emphasizes the requirement for a well-packed hydrophobic interior, but minimizes the importance of the exterior, provided it is hydrophilic. We demonstrate that the exterior plays a significant role when a globular protein is studied under physiologically relevant conditions. By changing a surface residue we show that attractive interactions between the protein surface and the cytosol modulate the stability of the protein, even though the change has a negligible effect in dilute solution. Recognizing and quantifying such intracellular interactions will aid in understanding and manipulating the biological role of proteins. Protein quinary interactions organize the cellular interior and its metabolism. Although the interactions stabilizing secondary, tertiary, and quaternary protein structure are well defined, details about the protein-matrix contacts that comprise quinary structure remain elusive. This gap exists because proteins function in the crowded cellular environment, but are traditionally studied in simple buffered solutions. We use NMR-detected H/D exchange to quantify quinary interactions between the B1 domain of protein G and the cytosol of Escherichia coli. We demonstrate that a surface mutation in this protein is 10-fold more destabilizing in cells than in buffer, a surprising result that firmly establishes the significance of quinary interactions. Remarkably, the energy involved in these interactions can be as large as the energies that stabilize specific protein complexes. These results will drive the critical task of implementing quinary structure into models for understanding the proteome.
关键词：H/D exchange ; quinary interactions ; protein NMR ; protein thermodynamics
