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A study on the effect of surface lysine to arginine mutagenesis on protein stability and structure using green fluorescent protein.

ABSTRACT: Two positively charged basic amino acids, arginine and lysine, are mostly exposed to protein surface, and play important roles in protein stability by forming electrostatic interactions. In particular, the guanidinium group of arginine allows interactions in three possible directions, which enables arginine to form a larger number of electrostatic interactions compared to lysine. The higher pKa of the basic residue in arginine may also generate more stable ionic interactions than lysine. This paper reports an investigation whether the advantageous properties of arginine over lysine can be utilized to enhance protein stability. A variant of green fluorescent protein (GFP) was created by mutating the maximum possible number of lysine residues on the surface to arginines while retaining the activity. When the stability of the variant was examined under a range of denaturing conditions, the variant was relatively more stable compared to control GFP in the presence of chemical denaturants such as urea, alkaline pH and ionic detergents, but the thermal stability of the protein was not changed. The modeled structure of the variant indicated putative new salt bridges and hydrogen bond interactions that help improve the rigidity of the protein against different chemical denaturants. Structural analyses of the electrostatic interactions also confirmed that the geometric properties of the guanidinium group in arginine had such effects. On the other hand, the altered electrostatic interactions induced by the mutagenesis of surface lysines to arginines adversely affected protein folding, which decreased the productivity of the functional form of the variant. These results suggest that the surface lysine mutagenesis to arginines can be considered one of the parameters in protein stability engineering.

SUBMITTER: Sokalingam S

PROVIDER: S-EPMC3392243 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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A study on the effect of surface lysine to arginine mutagenesis on protein stability and structure using green fluorescent protein.

Sokalingam Sriram S Raghunathan Govindan G Soundrarajan Nagasundarapandian N Lee Sun-Gu SG

PloS one 20120709 7

Two positively charged basic amino acids, arginine and lysine, are mostly exposed to protein surface, and play important roles in protein stability by forming electrostatic interactions. In particular, the guanidinium group of arginine allows interactions in three possible directions, which enables arginine to form a larger number of electrostatic interactions compared to lysine. The higher pKa of the basic residue in arginine may also generate more stable ionic interactions than lysine. This pa ...[more]

PMID: 22792305

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Project description:BackgroundHorseradish Peroxidase (HRP) plays important roles in many biotechnological fields, including diagnostics, biosensors and biocatalysis. Often, it is used in immobilised form. With conventional immobilisation techniques, the enzyme adheres in random orientation: the active site may face the solid phase rather than bulk medium, impeding substrate access and leading to sub-optimal catalytic performance. The ability to immobilise HRP in a directional manner, such that the active site would always face outwards from the insoluble matrix, would maximise the immobilised enzyme's catalytic potential and could increase HRP's range of actual and potential applications.ResultsWe have replaced arginine residues on the face of glycan-free recombinant HRP opposite to the active site by lysines. Our strategy differs from previous reports of specific HRP immobilisation via an engineered affinity tag or single reactive residue. These conservative Arg-to-Lys substitutions provide a means of multipoint covalent immobilisation such that the active site will always face away from the immobilisation matrix. One triple and one pentuple mutant were generated by substitution of solvent-exposed arginines on the "back" of the polypeptide (R118, R159 and R283) and of residues known to influence stability (K232 and K241). Orientated HRP immobilisation was demonstrated using a modified polyethersulfone (PES) membrane; the protein was forced to orientate its active site away from the membrane and towards the bulk solution phase. Mutant properties and bioinformatic analysis suggested the reversion of K283R to improve stability, thus generating two additional mutants (K118/R159K and R118K/K232N/K241F/R283K). While most mutants were less stable in free solution than wild type rHRP, the quadruple revertant regained some stability over its mutant counterparts. A greater degree of immobilisation on CNBr-activated Sepharosetrade mark was noted with increased lysine content; however, only marginal gains in solvent stability resulted from immobilisation on this latter matrix.ConclusionDirectional, orientated, immobilisation of rHRP mutants onto an activated, modified polyethersulfone membrane has been achieved with excellent retention of catalytic activity; however, re-engineering of acceptable stability characteristics into the "immobilisation mutants" will determine their applicability in diagnosis and biosensor development.

Dataset Information

A study on the effect of surface lysine to arginine mutagenesis on protein stability and structure using green fluorescent protein.

Publications

A study on the effect of surface lysine to arginine mutagenesis on protein stability and structure using green fluorescent protein.

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