Complementation of peptides of barnase, extracellular ribonuclease of Bacillus amyloliquefaciens.

Recovery of ribonuclease activity by complementation of peptides of barnase is reported. Activity is restored to barnase-(1-102), which lacks eight amino acids from its COOH terminus, by combination with peptides-(88-110), -(95-110), or -(99-108), and also with succinylated peptide-(88-110). The dissociation constants are about 8 X 10(-6) M for the first two combinations and little, if any, greater for the other two. Based on barnase-(1-102) concentration, up to 80% of native activity is obtained with peptide-(88-110) but only 5 to 20% with the others. The octapeptide-(103-110), equivalent to the residues missing from barnase-(1-102), does not complement barnase-(1-102), suggesting that an intact sequence about His-102 and Tyr-103 is required for activity. Barstar, the natural inhibitor of barnase, completely inhibits all activity of the complementing peptides.