1hev

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HEVEIN: THE NMR ASSIGNMENT AND AN ASSESSMENT OF SOLUTION-STATE FOLDING FOR THE AGGLUTININ-TOXIN MOTIF

Overview

The first high-resolution solution-state structure of a member of the, toxin-agglutinin folding motif with the WGA disulfide linkage is, presented. The 1H NMR spectrum of hevein has been 100% assigned from, residue 2 through residue 43, the C-terminus, using two-dimensional, correlation and NOE spectroscopy. During the course of the NOESY analysis, the three-dimensional structural features of hevein were derived, using, nonstereospecific distance constraints (with tight bounds) for XPLOR, simulated annealing followed by unconstrained relaxation in the CHARMm, force field, at two levels of long-range constraint density. In addition, a large number of low-bound-only constraints, corresponding to unobserved, NOE's, were used in both refinements. The first structure elucidation, employed a total of 180 distance constraints (60 of which were medium or, long range, i/i+n with n < or = 2). The second refinement employed 244, (101 medium or long range) constraints: some conformation-insensitive, intraresidue constraints were deleted, two misassigned long-range, constraints were corrected, and 41 new i/i+n (n > or = 2) constraints were, added. The average bounds precisions of the two refinements were, comparable (+/- 0.44 A) and significantly tighter than those that result, when a universal low bound corresponding to the sum of the van der Waals, radii was used. (The more conservative treatment of NOE's gave the same, final structure but required a higher constraint density before assignment, errors would stand out during the refinement.) Constraint density also has, a significant influence on convergence and accuracy using tight, constraints. The study demonstrates that convergence within an ensemble of, solution structures is not a dependable criterion for either the accuracy, or precision of the derived structure. The best fitting conformers from, the refinement at the higher constraint density bear a greater similarity, to the solid-state structure of the domains of wheat germ agglutinin (0.95, A rmsd over residues 2-32) than to the recently reported 2.8-A X-ray, structure of hevein (1.25 A rmsd over residues 2-32, 2.83 A rmsd over, residues 2-42). The consensus conformer from the solution data is defined, to a backbone rmsd of < 0.6 A over the full sequence for which NMR data, could be collected.(ABSTRACT TRUNCATED AT 400 WORDS)

About this Structure

1HEV is a Single protein structure of sequence from Hevea brasiliensis. Full crystallographic information is available from OCA.

Reference

Hevein: NMR assignment and assessment of solution-state folding for the agglutinin-toxin motif., Andersen NH, Cao B, Rodriguez-Romero A, Arreguin B, Biochemistry. 1993 Feb 16;32(6):1407-22. PMID:8431421

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