Towards the glycoproteome of Mycobacterium tuberculosis

Abstract

Tuberculosis continues to be a major threat to public health having one of the highest mortalities of any infectious disease despite the use of antibacterial therapy and a partially effective vaccine. Mycobacterium tuberculosis has a complex relationship with its host that is mediated in part by glycosylated proteins, but knowledge about the glycoproteome of tuberculosis is still lacking. In fact, the glycostructures are currently known only for two glycoproteins (alanine and proline rich secreted protein APA and superoxide dismutase SODC).To identify potentially glycosylated proteins in M. tuberculosis, we investigated mycobacterial subcellular fractions (cell wall, cell membrane and culture filtrate proteins) using the following lectins: Concanavalin A (ConA), Soybean Agglutinin (SBA), and Wheat Germ Agglutinin (WGA) followed by liquid chromatography‐mass spectrometry approaches and bioinformatic analyses.As expected, there was some overlap between the different lectins in their ability to bind potential glycoproteins. Interestingly, there was no general trend in that one lectin may be better than another. In fact, ConA identified the most glycoprotein candidates in CFP but the least in cell wall and membrane. SBA identified the most candidates in the cell wall whereas WGA identified the largest number of potential glycoproteins from the cell membrane..To validate the presence of glycoproteins, several strategies were pursued including collision induced dissociation and electron transfer dissociation techniques, novel bioinformatics analyses involving a novel virtual neutral loss algorithm and statistical analysis of enrichment in cell fractions with and without lectin treatment.