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Barnase, a member of the family of homologous microbial ribonucleases, catalyses the cleavage of single-stranded RNA via a two-step mechanism thought to be similar to that of pancreatic ribonuclease. The mechanism involves a transesterification to give a 2', 3'-cyclic phosphate intermediate, followed by hydrolysis to yield a 3' nucleotide. The active site residues His and Glu act as general acid-base groups during catalysis, while the Arg and Lys residues are important in binding the reactive phosphate, the latter probably binding the phosphate in the transition state. Barstar, a small 89 residue intracellular protein is a natural inhibitor of Barnase.
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Jiyao W et al.(2023). "The conserved domain database in 2023.",