Journal
JOURNAL OF BIOLOGICAL CHEMISTRY
Volume 275, Issue 4, Pages 2931-2937Publisher
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.275.4.2931
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- NIAID NIH HHS [AI38335] Funding Source: Medline
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Herpes simplex virus type-1 origin-binding protein (UL9 protein) initiates viral replication by unwinding the origins. It possesses sequence specific DNA-binding activity, single-stranded DNA-binding activity, DNA helicase activity, and ATPase activity that is strongly stimulated by single-stranded DNA. We have examined the role of cysteines in its action as a DNA helicase, The DNA helicase and DNA-dependent ATPase activities of UL9 protein were stimulated by reducing agent and specifically inactivated by the sulfhydryl-specific reagent N-ethyhmaleimide, To identify the cysteine responsible for this phenomenon, a conserved cysteine in the vicinity of the ATP-binding site (cysteine 111) was mutagenized to alanine, UL9C111A. protein exhibits defects in its DNA helicase and DNA-dependent ATPase activities and was unable to support origin-specific DNA replication in vivo. A kinetic analysis indicates that these defects are due to the inability of single-stranded DNA to induce high affinity ATP binding in UL9C111A protein. The DNA-dependent ATPase activity of UL9C111A protein is resistant to N-ethylmaleimide, while its DNA helicase activity remains sensitive. Accordingly, sensitivity of UL9 protein to N-ethylmaleimide is due to at least two cysteines, Cysteine 111 is involved in coupling single-stranded DNA binding to ATP-binding and subsequent hydrolysis, while a second cysteine is involved in coupling ATP hydrolysis to DNA unwinding.
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