Interface barnase-barstar

Interactions Analysis of the Barnase-Barstar Interface by Single Mutations and Double Mutant Cycles. 

Schreiber G, Fersht AR (1995) Energetics of protein-protein interactions analysis of the barnase-barstar interface by single mutations and double mutant cycles, J Mol Biol, 248 -178 1X9... 

In the barnase-barstar system, there is a selective pressure on the kinetics of association, the ribonuclease activity being lethal if expressed in the cell. The genes form an operon and, when both proteins are produced together in the bacterium, barnase must be either excreted or immediately inhibited by barstar. Unlike the selection for tight binding, which operates almost exclusively on residues at the interface, the selection for fast binding acts on all charged residues of the two proteins. 

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