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Electrostatic Properties of Protein-Protein Complexes

Computational Biophysics and Bioinformatics, Department of Physics and Astronomy, Clemson University, Clemson, South Carolina 29634

Correspondence: Address reprint requests to Emil Alexov, E-mail: ealexov{at}clemson.edu.

Statistical electrostatic analysis of 37 protein-protein complexes extracted from the previously developed database of protein complexes (ProtCom, http://www.ces.clemson.edu/compbio/protcom) is presented. It is shown that small interfaces have a higher content of charged and polar groups compared to large interfaces. In a vast majority of the cases the average pK_a shifts for acidic residues induced by the complex formation are negative, indicating that complex formation stabilizes their ionizable states, whereas the histidines are predicted to destabilize the complex. The individual pK_a shifts show the same tendency since 80% of the interfacial acidic groups were found to lower their pK_as, whereas only 25% of histidines raise their pK_a upon the complex formation. The interfacial groups have been divided into three sets according to the mechanism of their pK_a shift, and statistical analysis of each set was performed. It was shown that the optimum pH values (pH of maximal stability) of the complex tend to be the same as the optimum pH values of the complex components. This finding can be used in the homology-based prediction of the 3D structures of protein complexes, especially when one needs to evaluate and rank putative models. It is more likely for a model to be correct if both components of the model complex and the entire complex have the same or at least similar values of the optimum pH.

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				K. Brock, K. Talley, K. Coley, P. Kundrotas, and E. Alexov Optimization of Electrostatic Interactions in Protein-Protein Complexes Biophys. J., November 15, 2007; 93(10): 3340 - 3352. [Abstract] [Full Text] [PDF]