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 A 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.
Molecular Biology Program, Sloan-Kettering Institute, New York, NY 10021, USA.
Li Kai
LK
Wang
Christopher D
CD
Lima
Stewart
S
Shuman
D000595:Amino Acid Sequence; D017122:Bacteriophage T4 / Q000201:enzymology*; D001665:Binding Sites; D002384:Catalysis; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011116:Polynucleotide 5'-Hydroxyl-Kinase / Q000737:chemistry* / Q000378:metabolism*; D020836:Protein Structure, Quaternary; D017386:Sequence Homology, Amino Acid
D011116:Polynucleotide 5'-Hydroxyl-Kinase