The thumb's knuckle. Flexibility in the thumb subdomain of T7 RNA polymerase is revealed by the structure of a chimeric T7/T3 RNA polymerase.
We have solved the structure of a chimeric T7/T3 RNA polymerase (RNAP) in an orthorhombic crystal by molecular replacement with the T7 RNAP structure determined from a monoclinic crystal. The structure of the protruding "thumb" subdomain of the polymerase appears very different in these two crystals apparently because of differences in packing contacts made by the thumb subdomain. These observations support the proposal that the thumb subdomain is flexible and can wrap around bound template to obstruct polymerase: template dissociation during processive synthesis.
Department of Biochemistry, University of Texas Health Science Center, San Antonio 78284-7862.
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Sousa
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Wang
D000595:Amino Acid Sequence; D017903:Bacteriophage T3 / Q000201:enzymology* / Q000235:genetics; D017123:Bacteriophage T7 / Q000201:enzymology* / Q000235:genetics; D018360:Crystallography, X-Ray; D012321:DNA-Directed RNA Polymerases / Q000737:chemistry* / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D014764:Viral Proteins
D011993:Recombinant Fusion Proteins; D014764:Viral Proteins; C081591:bacteriophage T3 RNA polymerase; C062210:bacteriophage T7 RNA polymerase; D012321:DNA-Directed RNA Polymerases