title: Improved sequence-based prediction of protein secondary structures by combining vacuum-ultraviolet circular dichroism spectroscopy with neural network.
abstract: Synchrotron-radiation vacuum-ultraviolet circular dichroism (VUVCD) spectroscopy can significantly improve the predictive accuracy of the contents and segment numbers of protein secondary structures by extending the short-wavelength limit of the spectra. In the present study, we combined VUVCD spectra down to 160 nm with neural-network (NN) method to improve the sequence-based prediction of protein secondary structures. The secondary structures of 30 target proteins (test set) were assigned into alpha-helices, beta-strands, and others by the DSSP program based on their X-ray crystal structures. Combining the alpha-helix and beta-strand contents estimated from the VUVCD spectra of the target proteins improved the overall sequence-based predictive accuracy Q(3) for three secondary-structure components from 59.5 to 60.7%. Incorporating the position-specific scoring matrix in the NN method improved the predictive accuracy from 70.9 to 72.1% when combining the secondary-structure contents, to 72.5% when combining the numbers of segments, and finally to 74.9% when filtering the VUVCD data. Improvement in the sequence-based prediction of secondary structures was also apparent in two other indices of the overall performance: the correlation coefficient (C) and the segment overlap value (SOV). These results suggest that VUVCD data could enhance the predictive accuracy to over 80% when combined with the currently best sequence-prediction algorithms, greatly expanding the applicability of VUVCD spectroscopy to protein structural biology.
authors.affiliation: Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Matsuo
authors.forename: Hidenori
authors.initials: H
authors.lastname: Watanabe
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Gekko
mesh_terms: D000465:Algorithms; D000595:Amino Acid Sequence; D000818:Animals; D002942:Circular Dichroism / Q000379:methods*; D006801:Humans; D016571:Neural Networks, Computer; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet / Q000379:methods*
chemical_list: D011506:Proteins