Domain architecture and functional prediction

NCBI Conserved Domain Database (CDD) (Lu et al. 2020) and InterPro server (Blum et al. 2021) were used to identify the various domains present in the protein sequence of the signature and to predict its function. Putative substrate binding sites of the domains were inferred from NCBI CDD. The Transporter Substrate Specificity Prediction (TrSSP) server was used to determine the substrate level specificity of the signature protein (Mishra et al. 2014). Support vector machine (SVM)-based computational models utilising amino acid index and position-specific scoring matrix (PSSM) profiles were used to predict the substrate level of signature for seven different transporter classes (amino acid, anion, cation, electron, protein/mRNA, sugar, and other transporters). The predicted signature was also inspected using a model that discriminates transporters from non-transporters.