RNA repair enzyme: T4 polynucleotide kinase

Structure and mechanism of T4 polynucleotide kinase: an RNA repair enzyme: "T4 polynucleotide kinase (Pnk), in addition to being an invaluable research tool, exemplifies a family of bifunctional enzymes with 5'-kinase and 3'-phosphatase activities that play key roles in RNA and DNA repair.

T4 Pnk is a homotetramer composed of a C-terminal phosphatase domain and an N-terminal kinase domain. The 2.0 Å crystal structure of the isolated kinase domain highlights a tunnel-like active site through the heart of the enzyme, with an entrance on the 5' OH acceptor side that can accommodate a single-stranded polynucleotide. The active site is composed of essential side chains that coordinate the beta phosphate of the NTP donor and the 3' phosphate of the 5' OH acceptor, plus a putative general acid that activates the 5' OH. The structure rationalizes the different specificities of T4 and eukaryotic Pnk and suggests a model for the assembly of the tetramer.

Li Kai Wang1, Christopher D. Lima2 and Stewart Shuman1
Structure and mechanism of T4 polynucleotide kinase: an RNA repair enzyme
The EMBO Journal (2002) 21, 3873–3880, doi: 10.1093/emboj/cdf397
Subject Categories: Structural Biology Genome Stability & Dynamics