BARNASE MUTANT SER57ALA - PRODUCTION AND PROPERTIES

Barnase, an extracellular ribonuclease of Bacillus amyloliquefaciens, is a purine-specific enzyme with clear preference for the guanylic bas e, especially with short substrates. The work was aimed at ascertainin g the role of Ser-57 in the ''recognition loop'' of the RNase in the m olecular mechanism of substrate discrimination. The mutant protein wit h the Ser57 Ala change was expressed in Escherichia coli and used to d etermine the kinetic parameters of polymeric substrate hydrolysis. The amino acid change was found to have no dramatic effect on polynucleot ide cleavage.