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[Barnase mutant Ser57Ala: preparation and properties]
E Iu Kolbanovskaia1, A L Okorokov, K I Panov
1National Institute of Health, Bethesda, Md. 20892.
Molekuliarnaia Biologiia
|May 1, 1994
Summary
Researchers investigated barnase, an enzyme that breaks down RNA. Mutating a specific amino acid (Ser-57) in barnase did not significantly alter its RNA hydrolysis kinetics, suggesting this residue is not critical for polynucleotide cleavage.
Area of Science:
- Biochemistry
- Molecular Biology
- Enzymology
Background:
- Barnase is an extracellular ribonuclease from Bacillus amyloliquefaciens.
- It belongs to a family of small microbial ribonucleases with conserved structures and functions.
- Barnase hydrolyzes phosphodiester bonds in RNA, primarily at guanosine nucleotides.
Purpose of the Study:
- To investigate the molecular basis of barnase's guanylic specificity.
- To determine the role of Ser-57 in the "base recognition loop" of barnase.
- To analyze the effect of Ser-57 mutation on the enzyme's kinetic properties.
Main Methods:
- Site-directed mutagenesis was used to replace Ser-57 with Alanine in barnase.
- The mutant barnase protein was expressed in an Escherichia coli system.
- Kinetic parameters of polynucleotide hydrolysis by the mutant enzyme were studied.
Main Results:
- Mutation of Ser-57 to Alanine in the "base recognition loop" of barnase was successfully created.
- The mutant barnase protein was purified and characterized.
- The kinetic parameters for the hydrolysis of polynucleotide substrates by the Ser-57 mutant were not significantly affected.
Conclusions:
- The Ser-57 residue in the "base recognition loop" of barnase is not essential for the catalytic hydrolysis of polynucleotide substrates.
- The guanylic specificity of barnase in polynucleotide hydrolysis may not be solely dependent on this specific residue.
- Further studies are needed to elucidate the precise molecular mechanisms underlying barnase's substrate specificity.