Number of selected features after one-step and two-step mRMR feature selection for 5-class prediction.

Feature selection was performed based on benchmark datasets. CLF, MF, PF, CF and CRYS represent assignment of 5-class experimental steps. A denotes the one-step mRMR feature selection. B denotes the two-step mRMR feature selection. AA (amino acid) composition denotes the 20 standard amino acid compositions. Exposure-related information: the features integrate the predicted exposed residue information. Burial-related information: the features integrate the predicted exposed residue information. AAindex 1 & Exposed: average values of physicochemical properties using the amino acid index (AAindex 1) in all the predicted exposed residues (Table S2). AAindex1 & Buried: average values of physicochemical properties using the amino acid index (AAIndex1) in all the predicted buried residues. AA types & Exposed/Buried: frequency of the 20 standard AAs (type 1), hydrophobic/hydrophilic/neutral/position/negative AAs (type 2) and AA groups (type 3) in all predicted exposed or buried residues. Exposure/burial ratio: ratio of the features integrating the predicted exposed residue information to that integrating the predicted buried residue information. Percentage of AA index-related features denotes the frequency of AA index-related features within the selected set. Further explanations are included in Table S2.