Networks of high mutual information define the structural proximity of catalytic sites: implications for catalytic residue identification

• Published in: PLoS computational biology Vol. 6; no. 11; p. e1000978
• Main Authors: Marino Buslje, Cristina, Teppa, Elin, Di Doménico, Tomas, Delfino, José María, Nielsen, Morten
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 04-11-2010; Public Library of Science (PLoS)
• Subjects: Amino acids; Area Under Curve; Biochemistry; Biophysics/Biocatalysis; Biophysics/Biomacromolecule-Ligand Interactions; Catalysis; Catalytic Domain; Computational Biology; Computational Biology - methods; Computational Biology/Comparative Sequence Analysis; Computational Biology/Evolutionary Modeling; Computational Biology/Macromolecular Sequence Analysis; Computational Biology/Macromolecular Structure Analysis; Computational Biology/Protein Homology Detection; Computational Biology/Protein Structure Prediction; Computational Biology/Sequence Motif Analysis; Databases, Protein; Enzymes; Enzymes - chemistry; Enzymes - metabolism; Evolution; Hypotheses; Models, Molecular; Models, Statistical; Neural networks; Physiological aspects; Properties; Protein Conformation; Proteins; Reproducibility of Results; Sequence Homology; Denmark; Sequence Homology; Enzymes; Catalytic Domain; Reproducibility of Results; Area Under Curve; Databases, Protein; Computational Biology; Models, Molecular; Protein Conformation; Models, Statistical
• ISSN: 1553-7358; 1553-734X; 1553-7358
• DOI: 10.1371/journal.pcbi.1000978

Identification of catalytic residues (CR) is essential for the characterization of enzyme function. CR are, in general, conserved and located in the functional site of a protein in order to attain their function. However, many non-catalytic residues are highly conserved and not all CR are conserved throughout a given protein family making identification of CR a challenging task. Here, we put forward the hypothesis that CR carry a particular signature defined by networks of close proximity residues with high mutual information (MI), and that this signature can be applied to distinguish functional from other non-functional conserved residues. Using a data set of 434 Pfam families included in the catalytic site atlas (CSA) database, we tested this hypothesis and demonstrated that MI can complement amino acid conservation scores to detect CR. The Kullback-Leibler (KL) conservation measurement was shown to significantly outperform both the Shannon entropy and maximal frequency measurements. Residues in the proximity of catalytic sites were shown to be rich in shared MI. A structural proximity MI average score (termed pMI) was demonstrated to be a strong predictor for CR, thus confirming the proposed hypothesis. A structural proximity conservation average score (termed pC) was also calculated and demonstrated to carry distinct information from pMI. A catalytic likeliness score (Cls), combining the KL, pC and pMI measures, was shown to lead to significantly improved prediction accuracy. At a specificity of 0.90, the Cls method was found to have a sensitivity of 0.816. In summary, we demonstrate that networks of residues with high MI provide a distinct signature on CR and propose that such a signature should be present in other classes of functional residues where the requirement to maintain a particular function places limitations on the diversification of the structural environment along the course of evolution.