Primary Citation of Related Structures: 1RDA, 1RDB, 1RDC
PubMed Abstract:
In order to investigate the relationships between the three-dimensional structure and the enzymic activity of E. coli RNase HI, three mutant proteins, which were completely inactivated by the replacements of three functional residues, Asp10 by Asn (D10N), Glu48 by Gln (E48Q), and Asp70 by Asn (D70N), were crystallized ...
In order to investigate the relationships between the three-dimensional structure and the enzymic activity of E. coli RNase HI, three mutant proteins, which were completely inactivated by the replacements of three functional residues, Asp10 by Asn (D10N), Glu48 by Gln (E48Q), and Asp70 by Asn (D70N), were crystallized. Their three-dimensional structures were determined by x-ray crystallography. Although the entire backbone structures of these mutants were not affected by the replacements, very localized conformational changes were observed around the Mg(2+)-binding site. The substitution of an amide group for a negatively charged carboxyl group in common induces the formation of new hydrogen bond networks, presumably due to the cancellation of repulsive forces between carboxyl side chains with negative charges. These conformational changes can account for the loss of the enzymic activity in the mutants, and suggest a possible role for Mg2+ in the hydrolysis. Since the 3 replaced acidic residues are completely conserved in sequences of reverse transcriptases from retroviruses, including human immunodeficiency virus, the concepts of the catalytic mechanism deduced from this structural analysis can also be applied to RNase H activity in reverse transcriptases.
Related Citations:
Structural Details of Ribonuclease H from Escherichia Coli as Refined to an Atomic Resolution Katayanagi, K., Miyagawa, M., Matsushima, M., Ishikawa, M., Kanaya, S., Nakamura, H., Ikehara, M., Matsuzaki, T., Morikawa, K. (1992) J Mol Biol 223: 1029
Three-Dimensional Structure of Ribonuclease H from E. Coli Katayanagi, K., Miyagawa, M., Matsushima, M., Ishikawa, M., Kanaya, S., Ikehara, M., Matsuzaki, T., Morikawa, K. (1990) Nature 347: 306
Organizational Affiliation:
Protein Engineering Research Institute, Osaka, Japan.
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