Download MendeleyStructural, thermodynamic, and mutational analyses of a psychrotrophic RNase HI.
Tadokoro, T., You, D.J., Abe, Y., Chon, H., Matsumura, H., Koga, Y., Takano, K., Kanaya, S.(2007) Biochemistry 46: 7460-7468
- PubMed: 17536836
- DOI: https://doi.org/10.1021/bi7001423
- Primary Citation of Related Structures:
2E4L - PubMed Abstract:
Ribonuclease (RNase) HI from the psychrotrophic bacterium Shewanella oneidensis MR-1 was overproduced in Escherichia coli, purified, and structurally and biochemically characterized. The amino acid sequence of MR-1 RNase HI is 67% identical to that of E. coli RNase HI. The crystal structure of MR-1 RNase HI determined at 2.0 A resolution was highly similar to that of E. coli RNase HI, except that the number of intramolecular ion pairs and the fraction of polar surface area of MR-1 RNase HI were reduced compared to those of E. coli RNase HI. The enzymatic properties of MR-1 RNase HI were similar to those of E. coli RNase HI. However, MR-1 RNase HI was much less stable than E. coli RNase HI. The stability of MR-1 RNase HI against heat inactivation was lower than that of E. coli RNase HI by 19 degrees C. The conformational stability of MR-1 RNase HI was thermodynamically analyzed by monitoring the CD values at 220 nm. MR-1 RNase HI was less stable than E. coli RNase HI by 22.4 degrees C in Tm and 12.5 kJ/mol in DeltaG(H2O). The thermodynamic stability curve of MR-1 RNase HI was characterized by a downward shift and increased curvature, which results in an increased DeltaCp value, compared to that of E. coli RNase HI. Site-directed mutagenesis studies suggest that the difference in the number of intramolecular ion pairs partly accounts for the difference in stability between MR-1 and E. coli RNases HI.
Organizational Affiliation:
Department of Material and Life Science, Graduate School of Engineering, Osaka University, Suita, Japan.
