The positive training set was composed of human ɑ-helical TM domain-containing proteins appearing in at least two of the following three datasets: (i) the “high confidence” subset of the CSPA containing 735 proteins, (ii) the UniProtKB/Swiss-Prot (Version 2015_01) containing 2,043 proteins attributed with the “cell membrane” keyword, and (iii) the subcellular localization database COMPARTMENTS (69 (link)) containing 826 high-confidence plasma membrane proteins (five stars), which belong to the COMPARTMENTS inherent “plasma membrane” positive benchmark set and also belong to the COMPARTMENTS inherent negative benchmark sets for each of the remaining subcellular locations (all but “extracellular space”). Additional details can be found in SI Appendix, SI Methods.