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.