Proteomic Definition of the Cell Wall of Mycobacterium tuberculosis

Abstract

The cell envelope of Mycobacterium tuberculosis (Mtb) is complex and diverse; composed of proteins intermingled in a matrix of peptidoglycan, mycolic acids, lipids, and carbohydrates. Proteomic studies of the Mtb cell wall have been limited; nonetheless, the characterization of resident and secreted proteins associated with the cell wall are critical to understanding bacterial survival and immune modulation in the host. In this study, the cell wall proteome was defined in order to better understand its unique biosynthetic and secretion processes. Mtb cell wall was subjected to extraction with organic solvents to remove noncovalently bound lipids and lipoglycans and remaining proteins were solubilized with either SDS, Guanidine-HCl, or TX-114. These extracts were analyzed by two-dimensional gel electrophoresis and mass-spectrometry and resulted in the identification of 234 total proteins. The lipoproteome of Mtb, enriched in the TX-114 extract, was further resolved by multidimensional chromatography and mass spectrometry to identify an additional 294 proteins. A query of the 528 total protein identifications against Neural Network or Hidden Markov model algorithms predicted secretion signals in 87 proteins. Classification of these 528 proteins also demonstrated that 35% are involved in small molecule metabolism and 25% are involved in macromolecule synthesis and degradation building upon evidence that the Mtb cell wall is actively engaged in mycobacterial survival and remodeling.

An Unbiased Genome-Wide Mycobacterium tuberculosis Gene Expression Approach To Discover Antigens Targeted by Human T Cells Expressed during Pulmonary Infection

“…A subsequent literature search revealed that almost all further selected IVE-TB proteins (14 of the 16) have been identified previously in M. tuberculosis proteomic studies, confirming the protein expression of the M. tuberculosis genes identified in our study (44)(45)(46)(47)(48)(49)(50)(51)(52)(53)(54)(55)(56)(57) (Table III). Indeed, we observed that M. tuberculosis- FIGURE 3.…”

Label-free Quantitative Proteomics Reveals a Role for the Mycobacterium tuberculosis SecA2 Pathway in Exporting Solute Binding Proteins and Mce Transporters to the Cell Wall*

“…The largest functional groups of proteins identified are predicted to be involved in cell wall processes, intermediary metabolism/respiration, or are conserved hypothetical proteins (47). This distribution of cell wall-associated proteins among functional groups is similar to what is seen in other M. tuberculosis cell wall proteome studies (48,49).…”

Ergothioneine Is a Secreted Antioxidant in Mycobacterium smegmatis

“…In humans, the OCTN1 transporter is required for ERG transport into cells and involves cotransport of Na ϩ (18). This leads us to speculate that the ERG transporter in mycobacteria may be a member of the monovalent cation:proton antiporter family or the H ϩ /Na ϩ -translocating F-type, V-type, and A-type ATPase superfamily, which both utilize Na ϩ as a substrate (41). Since ERG has anti-inflammatory properties (15), the secretion of this molecule by M. tuberculosis may play a role in modulating the immune response by the host during infection and therefore warrants further investigation.…”