1cez
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(New page: 200px<br /><applet load="1cez" size="450" color="white" frame="true" align="right" spinBox="true" caption="1cez, resolution 2.40Å" /> '''CRYSTAL STRUCTURE OF...)
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Revision as of 10:17, 20 November 2007
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CRYSTAL STRUCTURE OF A T7 RNA POLYMERASE-T7 PROMOTER COMPLEX
Overview
Although the single-polypeptide-chain RNA polymerase from bacteriophage T7, (T7RNAP), like other RNA polymerases, uses the same mechanism of, polymerization as the DNA polymerases, it can also recognize a specific, promoter sequence, initiate new RNA chains from a single nucleotide, abortively cycle the synthesis of short transcripts, be regulated by a, transcription inhibitor, and terminate transcription. As T7RNAP is, homologous to the Pol I family of DNA polymerases, the differences between, the structure of T7RNAP complexed to substrates and that of the, corresponding DNA polymerase complex provides a structural basis for, understanding many of these functional differences. T7RNAP initiates RNA, synthesis at promoter sequences that are conserved from positions -17 to, +6 relative to the start site of transcription. The crystal structure at, 2.4 A resolution of T7RNAP complexed with a 17-base-pair promoter shows, that the four base pairs closest to the catalytic active site have melted, to form a transcription bubble. The T7 promoter sequence is recognized by, interactions in the major groove between an antiparallel beta-loop and, bases. The amino-terminal domain is involved in promoter recognition and, DNA melting. We have also used homology modelling of the priming and, incoming nucleoside triphosphates from the T7 DNA-polymerase ternary, complex structure to explain the specificity of T7RNAP for, ribonucleotides, its ability to initiate from a single nucleotide, and the, abortive cycling at the initiation of transcription.
About this Structure
1CEZ is a Single protein structure of sequence from Bacteriophage t7. Active as DNA-directed RNA polymerase, with EC number 2.7.7.6 Full crystallographic information is available from OCA.
Reference
Structural basis for initiation of transcription from an RNA polymerase-promoter complex., Cheetham GM, Jeruzalmi D, Steitz TA, Nature. 1999 May 6;399(6731):80-3. PMID:10331394
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