iSNO-AAPair: incorporating amino acid pairwise coupling into PseAAC for predicting cysteine S-nitrosylation sites in proteins

PeerJ. 2013 Oct 3;1:e171. doi: 10.7717/peerj.171. eCollection 2013.


As one of the most important and universal posttranslational modifications (PTMs) of proteins, S-nitrosylation (SNO) plays crucial roles in a variety of biological processes, including the regulation of cellular dynamics and many signaling events. Knowledge of SNO sites in proteins is very useful for drug development and basic research as well. Unfortunately, it is both time-consuming and costly to determine the SNO sites purely based on biological experiments. Facing the explosive protein sequence data generated in the post-genomic era, we are challenged to develop automated vehicles for timely and effectively determining the SNO sites for uncharacterized proteins. To address the challenge, a new predictor called iSNO-AAPair was developed by taking into account the coupling effects for all the pairs formed by the nearest residues and the pairs by the next nearest residues along protein chains. The cross-validation results on a state-of-the-art benchmark have shown that the new predictor outperformed the existing predictors. The same was true when tested by the independent proteins whose experimental SNO sites were known. A user-friendly web-server for iSNO-AAPair was established at, by which users can easily obtain their desired results without the need to follow the mathematical equations involved during its development.

Keywords: Nearest neighbor pair; Next nearest neighbor pair; Position-specific amino acid propensity; Post-translational modification; Pseudo amino acid composition; S-nitrosylation.

Grant support

This work is supported by the National Natural Science Foundation of China (No. 11301024, No. 11371365, No. 11101029, No. 31201002, No. 11071013, No. NCET-11-0574) and the Fundamental Research Funds for the Central Universities. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.