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'''1.6A CRYSTAL STRUCTURE OF POKEWEED ANTIVIRAL PROTEIN-III (PAP-III) WITH METHYLATED LYSINES''' | '''1.6A CRYSTAL STRUCTURE OF POKEWEED ANTIVIRAL PROTEIN-III (PAP-III) WITH METHYLATED LYSINES''' | ||
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[[Category: Phytolacca americana]] | [[Category: Phytolacca americana]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
[[Category: | [[Category: RRNA N-glycosylase]] | ||
[[Category: Kurinov, I V.]] | [[Category: Kurinov, I V.]] | ||
[[Category: Uckun, F M.]] | [[Category: Uckun, F M.]] | ||
[[Category: | [[Category: Pokeweed antiviral protein]] | ||
[[Category: | [[Category: Polynucleotide:adenosine]] | ||
[[Category: | [[Category: Ribosome inactivating protein]] | ||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 00:02:26 2008'' | |||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | |||
Revision as of 00:02, 3 May 2008
1.6A CRYSTAL STRUCTURE OF POKEWEED ANTIVIRAL PROTEIN-III (PAP-III) WITH METHYLATED LYSINES
OverviewOverview
Pokeweed antiviral protein III (PAP-III), a naturally occurring protein isolated from late summer leaves of the pokeweed plant (Phytolacca americana), has potent anti-HIV activity by an as yet undetermined molecular mechanism. PAP-III belongs to a family of ribosome-inactivating proteins that catalytically deadenylate ribosomal and viral RNA. The chemical modification of PAP-III by reductive methylation of its lysine residues significantly improved the crystal quality for X-ray diffraction studies. Trigonal crystals of the modified PAP-III, with unit cell parameters a=b=80.47A, c=76.21A, were obtained using 30% PEG400 as the precipitant. These crystals contained one enzyme molecule per asymmetric unit and diffracted up to 1.5A, when exposed to a synchrotron source. Here we report the X-ray crystal structure of PAP-III at 1.6A resolution, which was solved by molecular replacement using the homology model of PAP-III as a search model. The fold typical of other ribosome-inactivating proteins is conserved, despite several differences on the surface and in the loop regions. Residues Tyr(69), Tyr(117), Glu(172), and Arg(175) are expected to define the active site of PAP-III. Molecular modeling studies of the interactions of PAP-III and PAP-I with a single-stranded RNA heptamer predicted a more potent anti-HIV activity for PAP-III due to its unique surface topology and more favorable charge distribution in its 20A-long RNA binding active center cleft. In accordance with the predictions of the modeling studies, PAP-III was more potent than PAP-I in depurinating HIV-1 RNA.
About this StructureAbout this Structure
1LLN is a Single protein structure of sequence from Phytolacca americana. Full crystallographic information is available from OCA.
ReferenceReference
High resolution X-ray structure of potent anti-HIV pokeweed antiviral protein-III., Kurinov IV, Uckun FM, Biochem Pharmacol. 2003 May 15;65(10):1709-17. PMID:12754107 Page seeded by OCA on Sat May 3 00:02:26 2008