title: Structure of the RNA-dependent RNA polymerase of poliovirus.
abstract: BACKGROUND
  The central player in the replication of RNA viruses is the viral RNA-dependent RNA polymerase. The 53 kDa poliovirus polymerase, together with other viral and possibly host proteins, carries out viral RNA replication in the host cell cytoplasm. RNA-dependent RNA polymerases comprise a distinct category of polymerases that have limited sequence similarity to reverse transcriptases (RNA-dependent DNA polymerases) and perhaps also to DNA-dependent polymerases. Previously reported structures of RNA-dependent DNA polymerases, DNA-dependent DNA polymerases and a DNA-dependent RNA polymerase show that structural and evolutionary relationships exist between the different polymerase categories.
  
  
  RESULTS
  We have determined the structure of the RNA-dependent RNA polymerase of poliovirus at 2.6 A resolution by X-ray crystallography. It has the same overall shape as other polymerases, commonly described by analogy to a right hand. The structures of the 'fingers' and 'thumb' subdomains of poliovirus polymerase differ from those of other polymerases, but the palm subdomain contains a core structure very similar to that of other polymerases. This conserved core structure is composed of four of the amino acid sequence motifs described for RNA-dependent polymerases. Structure-based alignments of these motifs has enabled us to modify and extend previous sequence and structural alignments so as to relate sequence conservation to function. Extensive regions of polymerase-polymerase interactions observed in the crystals suggest an unusual higher order structure that we believe is important for polymerase function.
  
  
  CONCLUSIONS
  As a first example of a structure of an RNA-dependent RNA polymerase, the poliovirus polymerase structure provides for a better understanding of polymerase structure, function and evolution. In addition, it has yielded insights into an unusual higher order structure that may be critical for poliovirus polymerase function.
authors.affiliation: Department of Chemistry and Biochemistry, University of Colorado, Boulder 80309, USA.
authors.forename: J L
authors.initials: JL
authors.lastname: Hansen
authors.forename: A M
authors.initials: AM
authors.lastname: Long
authors.forename: S C
authors.initials: SC
authors.lastname: Schultz
mesh_terms: D000595:Amino Acid Sequence; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D008969:Molecular Sequence Data; D017955:Poliovirus / Q000201:enzymology*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012324:RNA-Dependent RNA Polymerase / Q000737:chemistry*
chemical_list: D012324:RNA-Dependent RNA Polymerase