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Kevin Keating Graduate
Student
kevin.keating@yale.edu
Low
Resolution RNA Crystallography using a Reduced Representation of RNA
RNA crystallography presents significant challenges not found in protein
crystallography. RNA crystals frequently diffract to lower resolutions than
protein crystals, and the RNA backbone contains six torsional angles per
nucleotide, as compared to two per amino acid along the protein backbone.
As a result, accurately solving RNA crystal structures can be difficult
and time-consuming. We are using a reduced representation of RNA to facilitate
this process. This reduced representation simplifies the RNA backbone into
two pseudotorsional angles per nucleotide, eta (C4′n-1, Pn, C4′n, Pn+1)
and theta (Pn, C4′n, Pn+1, C4′n+1) (1). These pseudotorsions depend on only
two atoms per residue, the phosphate and C4'. In addition, because the distance
between these two atoms is longer than the distance between two bonded atoms,
the pseudotorsional angles are less sensitive to inaccuracy in atom location
than the standard torsional angles. Thus, we are devising a method for solving
low resolution RNA crystal structures that uses pseudotorsions as a starting
point for determining the backbone structure. By examining how these pseudotorsions
relate to the standard torsional angles, we hope to develop an automated
procedure that can be used by crystallographers.
1. Duarte, C. & Pyle, A. M. (1998) JMB 284, 1465-1478
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