Quantitative proteomic analysis of mkl gene function in Mycobacterium marinum using iTRAQ

Objective: To identify differentially expressed proteins in Mycobacterium marinum wild-type (WT) and mkl::Tn mutant strains, and provide new clues for exploring the functions of mkl gene. Methods: Cellular proteins were extracted from cultures of M. marinum WT and mkl::Tn strains, and labelled with isobaric tags for relative and absolute quantitation (iTRAQ) 4-plex. Differentially expressed proteins were identified with LC-MS/MS and subjected to biological information analysis. Results: A total of 566 differentially expressed proteins were revealed, among which 232 proteins were up-regulated (ratio≥1.4) and 334 proteins were down-regulated (ratio≤0.7). These proteins are mainly associated with lipid metabolism, cell wall and cell processes, intermediary metabolism and respiration, and hypothetical proteins. The most down-regulated protein DesA3, is a fatty acid desaturase and involved in the synthesis of oleic acid. Further experiments showed that the growth of mkl::Tn strain was attenuated on 7H10-ADC agar plate without oleic acid, suggesting that mkl may play a role in the biosynthesis of oleic acid. Conclusion: Differentially expressed proteins were identified in M. marinum mkl::Tn compared to WT, and these results shed light on the mechanisms of mkl gene in mycobacterial pathogenesis.