Cell wall peptidolipids of Mycobacterium avium: from genetic prediction to exact structure of a nonribosomal peptide

Abstract

Mycobacteria have a complex cell wall structure that includes many lipids; however, even within a single subspecies of Mycobacterium avium these lipids can differ. Total lipids from an M. avium subsp. paratuberculosis (Map) ovine strain (S-type) contained no identifiable glycopeptidolipids or lipopentapeptide (L5P), yet both lipids are present in other M. avium subspecies. We determined the genetic and phenotypic basis for this difference using sequence analysis as well as biochemical and physico-chemical approaches. This strategy showed that a nonribosomal peptide synthase, encoded by mps1, contains three amino acid specifying modules in ovine strains, compared to five modules in bovine strains (C-type). Sequence analysis predicted these modules would produce the tripeptide Phe-N-Methyl-Val-Ala with a lipid moiety, termed lipotripeptide (L3P). Comprehensive physico-chemical analysis of Map S397 extracts confirmed the structural formula of the native L3P as D-Phe-N-Methyl-L-Val-L-Ala-OMe attached in N-ter to a 20-carbon fatty acid chain. These data demonstrate that S-type strains, which are more adapted in sheep, produce a unique lipid. There is a dose-dependent effect observed for L3P on upregulation of CD25+ CD8 T cells from infected cows, while L5P effects were static. In contrast, L5P demonstrated a significantly stronger induction of CD25+ B cells from infected animals compared to L3P.

Environmental Mycobacterium avium subsp. paratuberculosis Hosted by Free-Living Amoebae

“…Initially, the Map-S and Map-C type strains were distinguished based on their molecular fingerprints using IS 1311 polymorphism, MLSSR typing and hsp65 sequencing. However, beyond genetic typing, there are observed phenotypic differences including differences in their pigmentation, growth characteristics and lipopeptide structures in their cell walls (Bannantine et al, 2017 ). The environmental life cycle of Map is still poorly understood and at least one recent publication suggests that free-living amoebae (FLA) might be a potential environmental host (Salgado et al, 2015 ).…”

Lipids of Clinically Significant Mycobacteria

“…PLs based on a pentapeptide (L5P) and a tripeptide (L3P) were characterized (Fig. 17) (Bannantine et al 2017), the former in cattle M. paratuberculosis strains and the latter in sheep strains. A peptidolipid was isolated from cattle-associated "Mycobacterium minetti," a synonym of M. fortuitum, and given the name "fortuitine" (Vilkas et al 1963;Asselineau 1966).…”

Engineering Synthetic Lipopeptide Antigen for Specific Detection of Mycobacterium avium subsp. paratuberculosis Infection

“…According to genomic analysis, the S-type strains, which are more adapted in sheep, have evolved in two distinct subtype S-I and S-III (41). In a recent report we described that the SIII-type strain S397, produced a unique lipid, a tripeptide Phe-N-Methyl-Val-Ala with a N-ter lipid moiety, termed lipotripeptide (L3P) instead of the L5P detected in cattle strains (11). In addition, at the present time no L5P nor L3P has been detected in the lipids extracted from the S-I strain Telford that was used in the experimental sheep infections (data not shown).…”

“…It is an abundant molecule in Mycobacterium avium subsp. paratuberculosis (MAP) and found in the outermost layers of the cell envelope (8,11). Previously we deciphered the genetic organization, including the nonribosomal peptide synthase genes mps1, that participate in the biosynthesis of the peptidic moiety of the L5P (8).…”