Herpes simplex virus type 1 thymidine kinase SR39 mutant (HSV1-tk-SR39)

Mutant HSV thymidine kinase SR39 (HSV1-tk-SR39) is an engineered variant of the thymidine kinase enzyme from Herpes Simplex Virus type 1, optimized for enhanced substrate specificity and catalytic efficiency. This mutant features five specific amino acid substitutions (L159I, I160L, F161I, A167M, and G168A) in the nucleoside binding site, which significantly increase its affinity for acyclic guanosine analogs like ganciclovir and PET imaging tracers such as [18F]-FHBG (Gambhir et al., 2000, PNAS). In therapeutic applications, it functions as a suicide gene; when expressed in target cells via viral or non-viral vectors, it converts non-toxic prodrugs into cytotoxic metabolites that terminate DNA synthesis and trigger cell death (Black et al., 1996, PNAS). Beyond therapy, HSV1-tk-SR39 is a gold-standard reporter gene for positron emission tomography (PET), enabling researchers to track gene expression and cell-based therapies non-invasively in living subjects (Yaghoubi et al., 2006, Nature Protocols). Its dual role in therapy and diagnostics classifies it as a key tool in the field of theranostics, particularly for oncology and regenerative medicine.

Other names

HSV1-tk SR39SR39 mutantMutant HSV-1 thymidine kinaseHSV-tk SR39tk-SR39

The enzyme phosphorylates specific nucleoside analogs (prodrugs) into monophosphate forms, which are subsequently converted by host cellular kinases into toxic triphosphate metabolites that act as chain terminators, inhibit DNA polymerase, and induce apoptosis (Black et al., 1996, PNAS).