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| {{STRUCTURE_1e3h| PDB=1e3h | SCENE= }} | | {{STRUCTURE_1e3h| PDB=1e3h | SCENE= }} |
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| '''SEMET DERIVATIVE OF STREPTOMYCES ANTIBIOTICUS PNPASE/GPSI ENZYME'''
| | ===SEMET DERIVATIVE OF STREPTOMYCES ANTIBIOTICUS PNPASE/GPSI ENZYME=== |
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| ==Overview==
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| BACKGROUND: Polynucleotide phosphorylase (PNPase) is a polyribonucleotide nucleotidyl transferase (E.C.2.7.7.8) that degrades mRNA in prokaryotes. Streptomyces antibioticus PNPase also assays as a guanosine 3'-diphosphate 5'-triphosphate (pppGpp) synthetase (E.C.2.7.6.5). It may function to coordinate changes in mRNA lifetimes with pppGpp levels during the Streptomyces lifecycle. RESULTS: The structure of S. antibioticus PNPase without bound RNA but with the phosphate analog tungstate bound at the PNPase catalytic sites was determined by X-ray crystallography and shows a trimeric multidomain protein with a central channel. The structural core has a novel duplicated architecture formed by association of two homologous domains. The tungstate derivative structure reveals the PNPase active site in the second of these core domains. Structure-based sequence analysis suggests that the pppGpp synthetase active site is located in the first core domain. CONCLUSIONS: This is the first structure of a PNPase and shows the structural basis for the trimer assembly, the arrangement of accessory RNA binding domains, and the likely catalytic residues of the PNPase active site. A possible function of the trimer channel is as a contribution to both the processivity of degradation and the regulation of PNPase action by RNA structural elements.
| | The line below this paragraph, {{ABSTRACT_PUBMED_11080643}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 11080643 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_11080643}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Rna degradation]] | | [[Category: Rna degradation]] |
| [[Category: Rna processing]] | | [[Category: Rna processing]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 14:36:50 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 00:05:11 2008'' |
