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. 2008:2008:169-181.

A HAUSDORFF-BASED NOE ASSIGNMENT ALGORITHM USING PROTEIN BACKBONE DETERMINED FROM RESIDUAL DIPOLAR COUPLINGS AND ROTAMER PATTERNS

Affiliations

A HAUSDORFF-BASED NOE ASSIGNMENT ALGORITHM USING PROTEIN BACKBONE DETERMINED FROM RESIDUAL DIPOLAR COUPLINGS AND ROTAMER PATTERNS

Jianyang Michael Zeng et al. Comput Syst Bioinformatics Conf. 2008.

Abstract

High-throughput structure determination based on solution Nuclear Magnetic Resonance (NMR) spectroscopy plays an important role in structural genomics. One of the main bottlenecks in NMR structure determination is the interpretation of NMR data to obtain a sufficient number of accurate distance restraints by assigning nuclear Overhauser effect (NOE) spectral peaks to pairs of protons. The difficulty in automated NOE assignment mainly lies in the ambiguities arising both from the resonance degeneracy of chemical shifts and from the uncertainty due to experimental errors in NOE peak positions. In this paper we present a novel NOE assignment algorithm, called HAusdorff-based NOE Assignment (HANA), that starts with a high-resolution protein backbone computed using only two residual dipolar couplings (RDCs) per residue37, 39, employs a Hausdorff-based pattern matching technique to deduce similarity between experimental and back-computed NOE spectra for each rotamer from a statistically diverse library, and drives the selection of optimal position-specific rotamers for filtering ambiguous NOE assignments. Our algorithm runs in time O(tn(3) +tn log t), where t is the maximum number of rotamers per residue and n is the size of the protein. Application of our algorithm on biological NMR data for three proteins, namely, human ubiquitin, the zinc finger domain of the human DNA Y-polymerase Eta (pol η) and the human Set2-Rpb1 interacting domain (hSRI) demonstrates that our algorithm overcomes spectral noise to achieve more than 90% assignment accuracy. Additionally, the final structures calculated using our automated NOE assignments have backbone RMSD < 1.7 Å and all-heavy-atom RMSD < 2.5 Å from reference structures that were determined either by X-ray crystallography or traditional NMR approaches. These results show that our NOE assignment algorithm can be successfully applied to protein NMR spectra to obtain high-quality structures.

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Figures

Fig. 1
Fig. 1
Schematic illustration of the NOE assignment approach.
Fig. 2
Fig. 2
The NMR structures of ubiquitin, pol η and hSRI computed from our automatically-assigned NOEs. Panels A, B, C and D in first row show the structures of ubiquitin, Panels E, F and G in the middle row show the structures of pol η, and Panels H, I and J in the bottom row show the structures of hSRI. Panels A, E and H show the ensemble of 10 best NMR structures with minimum energies. The backbones are shown in red while the side-chains are shown in blue. Panels B, F and I show the ribbon view of the ensemble of structures. Panel D shows the backbone overlay of the mean structures (in blue color) of ubiquitin with its X-ray reference structures (in magenta color). The RMSD between the mean structure and the x-ray structure of ubiquitin is 1.23 Å for backbone atoms and 2.01 Å for all heavy atoms. Panels C, G and J show the backbone overlay of the mean structures (in blue color) with corresponding NMR reference structures (in green color) that have been deposited into the Protein Data Bank (PDB ID of ubiquitin: 1D3Z; PDB ID of pol η2: 2I5O; PDB ID of hSRI: 2A7O). The backbone RMSDs between the mean structures and the reference structures are 1.20 Å for ubiquitin, 1.38 Å for pol η, and 1.71 Å for hSRI. The all-heavy-atom RMSDs between the mean structures and the reference structures are 1.92 A for ubiquitin, 2.39 Å for pol η, and 2.43 Å for hSRI.

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