title: Importance of C-terminus of herpes simplex virus type 1 thymidine kinase for maintaining thymidine kinase and acyclovir-phosphorylation activities.
abstract: We previously isolated an acyclovir (ACV)-resistant herpes simplex virus type 1 (HSV-1), strain TAR, from a child with Wiskott-Aldrich syndrome. An acyclovir-sensitive HSV-1, strain TAS, had been isolated from the same patient before the isolation of HSV-1 TAR. The TK protein of ACV-sensitive HSV-1 TAS was composed of 376 amino acids, while that of HSV-1 TAR was composed of 407 amino acids with altered amino acid residue between positions 355-407. The elongation of TK was caused by a single nucleotide deletion of cytosine from a homopolymer stretch of 4 cytosine residues between positions 1061-1064. There was no viral TK activity in HSV-1 TAR-infected Vero cells, indicating the importance of the C-terminal portion of TK protein from positions 355-376. Recombinant TK polypeptides with amino acid deletions at the C-terminus were prepared, and TK and ACV-phosphorylation activities were examined. Deletion of 5 and 6 amino acids from the C-terminus of the TK polypeptide of HSV-1 TAS resulted in a reduction of TK activity by approximately 75% and 100%, respectively. These mutant TK polypeptides did not phosphorylate ACV. These results indicate that amino acid residues from positions 371-376 in the C-terminal portion of HSV-1 TK protein are essential for keeping TK and ACV-phosphorylation activities.
authors.affiliation: Special Pathogens Laboratory, Department of Virology 1, National Institute of Infectious Diseases, Musashimurayama, Tokyo, Japan. msaijo@nih.go.jp
authors.forename: Masayuki
authors.initials: M
authors.lastname: Saijo
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Suzutani
authors.forename: Masahiro
authors.initials: M
authors.lastname: Niikura
authors.forename: Shigeru
authors.initials: S
authors.lastname: Morikawa
authors.forename: Ichiro
authors.initials: I
authors.lastname: Kurane
mesh_terms: D000212:Acyclovir / Q000378:metabolism*; D000818:Animals; D000998:Antiviral Agents / Q000378:metabolism*; D002522:Chlorocebus aethiops; D018259:Herpesvirus 1, Human / Q000201:enzymology*; D006801:Humans; D016296:Mutagenesis; D010455:Peptides / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D013937:Thymidine Kinase / Q000235:genetics / Q000378:metabolism*; D014709:Vero Cells
chemical_list: D000998:Antiviral Agents; D010455:Peptides; D013937:Thymidine Kinase; D000212:Acyclovir