This old version of Proteopedia is provided for student assignments while the new version is undergoing repairs. Content and edits done in this old version of Proteopedia after March 1, 2026 will eventually be lost when it is retired in about June of 2026.
Apply for new accounts at the new Proteopedia. Your logins will work in both the old and new versions.
1lln
From Proteopedia
|
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
Page seeded by OCA on Thu Nov 8 14:17:19 2007
