1e3p: Difference between revisions

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.

1E3P is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Streptomyces_antibioticus Streptomyces antibioticus] with SO4 and WO4 as [http://en.wikipedia.org/wiki/ligands ligands]. Structure known Active Site: WO4. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1E3P OCA].  

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