Crystal structure of a DNA-dependent RNA polymerase (DNA primase)

Primases are essential components of the DNA replication apparatus in every organism. They catalyze the synthesis of oligoribonucleotides on single-st randed DNA, which subsequently serve as primers for the replicative DNA pol ymerases. In contrast to bacterial primases, the archaeal enzymes are close ly related to their eukaryotic counterparts. We have soh ed the crystal str ucture of the catalytic primase subunit from the hyperthermophilic archaeon Pyrococcus furiosus at 2.3 Angstrom resolution by multiwavelength anomalou s dispersion methods. The structure shows a two-domain arrangement with a n ovel zinc knuckle motif located in the primase (prim) domain. In this first structure of a complete protein of the archael/eukaryotic primase family, the arrangement of the catalytically active residue resembles the active si tes of various DNA polymerase that are unrelated in fold.