1lln
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(New page: 200px<br /> <applet load="1lln" size="450" color="white" frame="true" align="right" spinBox="true" caption="1lln, resolution 1.60Å" /> '''1.6A CRYSTAL STRUCT...)
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Revision as of 12:11, 8 November 2007
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1.6A CRYSTAL STRUCTURE OF POKEWEED ANTIVIRAL PROTEIN-III (PAP-III) WITH METHYLATED LYSINES
Overview
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 Structure
1LLN is a Single protein structure of sequence from Phytolacca americana. Active as rRNA N-glycosylase, with EC number 3.2.2.22 Full crystallographic information is available from OCA.
Reference
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
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