iBhb-Lys: Identify lysine β-hydroxybutyrylation sites using autoencoder feature representation and fuzzy SVM algorithm

Lysine β-hydroxybutyrylation (Kbhb) is newly discovered β-hydroxybutyrylate-derived histone modification which has been associated with the pathogenesis of many human diseases. To further elucidate the biological significance and molecular mechanism of Kbhb, it is necessary to accurately identify the Kbhb sites from protein sequences. In this study, a novel computational model named iBhb-Lys is developed for the identification of Kbhb sites. Four types of features are combined to encode each Kbhb site as a 3266-dimensional feature vector. And the autoencoder network is used to reduce the dimensionality of feature space, due to the high dimensionality of the combined features. In addition, to effectively reduce the influence of noise and outlier on classification, a new fuzzy support vector machine algorithm is proposed by incorporating the density around the sample into the fuzzy membership function. As illustrated by independent test, the AUC value of iBhb-Lys has increased by 2.22 % compared to the existing predictor KbhbXG. Feature analysis shows that some amino acid composition features, such as the occurrence frequency of leucine and histidine residues around Kbhb sites, contribute profoundly to the identification of Kbhb sites. The conclusions drawn in this study may provide useful reference for studying the molecular mechanism of Kbhb.