title: Fluctuations of backbone torsion angles obtained from NMR-determined structures and their prediction.
abstract: Protein molecules exhibit varying degrees of flexibility throughout their three-dimensional structures. Protein structural flexibility is often characterized by fluctuations in the Cartesian coordinate space. On the other hand, the protein backbone can be mostly defined by two torsion angles ϕ and ψ only. We introduce a new flexibility descriptor, backbone torsion-angle fluctuation derived from the variation of backbone torsion angles from different NMR models. The torsion-angle fluctuations correlate with mean-squared spatial fluctuations derived from the same collection of NMR models. We developed a neural-network based real-value predictor based on sequence information only. The predictor achieved ten-fold cross-validated correlation coefficients of 0.59 and 0.60, and mean absolute errors of 22.7° and 24.3° for the angle fluctuation of ϕ and ψ, respectively. This predictor is expected to be useful for function prediction and protein structure prediction when predicted torsion angles are used as restraints. Both sequence- and structure-based prediction of torsion-angle fluctuation will be available at http://sparks.informatics.iupui.edu within the SPINE-X package.
authors.affiliation: School of Informatics, Indiana University Purdue University, Indianapolis, Indiana 46202, USA.
authors.forename: Tuo
authors.initials: T
authors.lastname: Zhang
authors.forename: Eshel
authors.initials: E
authors.lastname: Faraggi
authors.forename: Yaoqi
authors.initials: Y
authors.lastname: Zhou
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D030562:Databases, Protein; D019906:Nuclear Magnetic Resonance, Biomolecular; D018583:Pliability; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry*; D015203:Reproducibility of Results; D012997:Solvents / Q000737:chemistry; D054159:Torsion, Mechanical
chemical_list: D000596:Amino Acids; D011506:Proteins; D012997:Solvents
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