1b21
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DELETION OF A BURIED SALT BRIDGE IN BARNASE
OverviewOverview
Double-mutant cycles are widely used in the field of protein engineering, to measure intermolecular and intramolecular interactions. Ideally, there, should be no structural rearrangement of the protein on making the two, single mutations and the double mutation within the cycle. However, structural pertubation on mutation does not preclude the use of this, method, providing the sum of the changes in the single mutants equals the, change in the double mutant. In this way, the energy associated with any, structural rearrangement cancels in the double-mutant cycle. Previously, the contribution of a buried salt bridge between Arg69 and Asp93 in, barnase to the stability of the folded protein has been determined by, double-mutant cycle analysis. In order to determine whether the measured, interaction of -14.0 kJ mol(-1) represents the true interaction energy, the crystal structure of each mutant within the double-mutant cycle was, solved. Although mutation results in structural shifts, the majority of, those in the single mutants are also found in the double mutant; their, energetic effects in the double-mutant cycle are therefore cancelled. This, study highlights the robust nature of the double-mutant cycle analysis.
About this StructureAbout this Structure
1B21 is a Single protein structure of sequence from Bacillus amyloliquefaciens with ZN as ligand. Active as Ribonuclease T(1), with EC number 3.1.27.3 Full crystallographic information is available from OCA.
ReferenceReference
A structural double-mutant cycle: estimating the strength of a buried salt bridge in barnase., Vaughan CK, Harryson P, Buckle AM, Fersht AR, Acta Crystallogr D Biol Crystallogr. 2002 Apr;58(Pt 4):591-600. Epub 2002, Mar 22. PMID:11914482
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