Structural and functional views of salt-bridge interactions of λ integrase in the higher order recombinogenic complexes visualized by genetic method

The integrase protein encoded by bacteriophage λ (Int) catalyzes site a specific DNA recombination by which the viral chromosome is inserted into and excised out of the host genome through the formation of higher order recombinogenic nucleoprotein complexes. Genetic and biochemical studies on the Int carried out by isolating “multimer-specific” mutants had revealed informative functional characteristics of specific electrostatic interactions occurring among the functional domains of Int. The λ Int recombination system shows the usefulness of structural and functional investigation of multimeric protein complexes through genetic studies on the electrostatic interactions of proteins comprising multimeric complexes. This approach is especially powerful when combined with NMR and X-ray crystallography results providing biological evidences of specific molecular interactions among proteins.

Research highlights
► This article reviews that biochemical and structural roles of specific salt-bridge interactions among the domains of bacteriophage λ integrase.
► Each salt-bridge interaction between the charged residues has highly specific functional roles in the higher order recombinogenic multiprotein complexes.
► Genetic and biochemical investigation of “multimer-specific” mutant proteins may be very useful in structural and functional characterizations of specific salt-bridge interactions of other multimeric protein complexes.