Contribution of surface salt bridges to protein stability.
The role of surface salt bridges in protein stabilization has been a source of controversy. Here we present the NMR structure of a hyperthermophilic rubredoxin variant (PFRD-XC4) and the thermodynamic analysis of two surface salt bridges by double mutant cycles. This analysis shows that the surface side chain to side chain salt bridge between Lys 6 and Glu 49 does not stabilize PFRD-XC4. The main chain to side chain salt bridge between the N-terminus and Glu 14 was, however, found to stabilize PFRD-XC4 by 1. 5 kcal mol(-)(1). The entropic cost of making a surface salt bridge involving the protein's backbone is reduced, since the backbone has already been immobilized upon protein folding.
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Biochemistry Option, California Institute of Technology, Pasadena, California 91125, USA.
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D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D018360:Crystallography, X-Ray; D019791:Guanidine; D006860:Hydrogen Bonding; D016297:Mutagenesis, Site-Directed; D019906:Nuclear Magnetic Resonance, Biomolecular; D011489:Protein Denaturation; D020027:Pyrococcus furiosus / Q000737:chemistry / Q000235:genetics; D012416:Rubredoxins / Q000737:chemistry* / Q000235:genetics; D012492:Salts / Q000737:chemistry; D012996:Solutions; D012997:Solvents / Q000737:chemistry; D013816:Thermodynamics
D001426:Bacterial Proteins; D012416:Rubredoxins; D012492:Salts; D012996:Solutions; D012997:Solvents; D019791:Guanidine