Crystal Structure of Thermus aquaticus Core RNA Polymerase at 3.3 Å Resolution (original) (raw)

Since the initial indications of DNA-dependent RNAP activity from a number of systems (Weiss and Gladstone, 1959; Huang et al., 1960; Hurwitz et al., 1960; Stevens, 1960) and the isolation of the RNAP enzyme from bacte-Summary rial sources (Chamberlin and Berg, 1962), a wealth of biochemical, biophysical, and genetic information has The X-ray crystal structure of Thermus aquaticus core accumulated on RNAP and its complexes with nucleic RNA polymerase reveals a "crab claw"-shaped moleacids and accessory factors (von Hippel et al., 1984; cule with a 27 Å wide internal channel. Located on the Erie et al., 1992; Sentenac et al., 1992; Gross et al., back wall of the channel is a Mg 2؉ ion required for 1996). Nevertheless, the enzyme itself, in terms of its catalytic activity, which is chelated by an absolutely structure-function relationship, remains a black box. An conserved motif from all bacterial and eukaryotic celessential step toward understanding the mechanism of lular RNA polymerases. The structure places key functranscription and its regulation is to determine threetional sites, defined by mutational and cross-linking dimensional structures of RNAP and its complexes with analysis, on the inner walls of the channel in close DNA, RNA, and regulatory factors. proximity to the active center Mg 2؉ . Further out from Low-resolution structures of bacterial and eukaryotic the catalytic center, structural features are found that RNAPs, provided by electron crystallography, reveal a may be involved in maintaining the melted transcripmolecule shaped like a crab claw with a groove or chantion bubble, clamping onto the RNA product and/or nel that is an appropriate size for accomodating double-DNA template to assure processivity, and delivering helical DNA (Darst et al., , 1998a(Darst et al., , 1998b; nucleotide substrates to the active center.