Reversion of a Moloney murine leukemia virus RNase H mutant at a second site restores enzyme function and infectivity.
The reverse transcriptase of retroviruses contains an RNase H activity essential for the proper synthesis of the viral DNA copy of the RNA genome. We have previously characterized a number of point mutations altering the RNase domain of the Moloney murine leukemia virus reverse transcriptase (S. W. Blain and S. P. Goff, J. Biol. Chem. 268:23585-23592, 1993). One such mutation, Y586F (a Y-to-F change at position 586), reduced RNase H activity, as assayed by in situ gel analysis, to about 5% of the wild-type level and prevented viral replication. We have now recovered a revertant virus with near-normal infectivity and in vitro enzymatic activity. The revertant contains a single substitution, N613H, distant in the primary sequence of the protein, but modeling with the Escherichia coli RNase H structure suggests that the reverted residue is close in space to the original substituted residue. Examination of the structure permits some suggestions as to how this second-site revertant restores enzyme activity.
Blain
S W
SW
Howard Hughes Medical Institute, Department of Biochemistry and Molecular Biophysics, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA.
Hendrickson
W A
WA
Goff
S P
SP
D001483:Base Sequence; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D017931:DNA Primers; D006868:Hydrolysis; D008969:Molecular Sequence Data; D008979:Moloney murine leukemia virus / Q000201:enzymology* / Q000472:pathogenicity; D009154:Mutation; D011487:Protein Conformation; D012313:RNA / Q000378:metabolism; D016914:Ribonuclease H / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
D017931:DNA Primers; D012313:RNA; D004247:DNA; D016914:Ribonuclease H