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![[Figure 1]](jb5039fig1mag.jpg)
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Figure 1
(a) The PIM/LM/LAM biosynthetic pathway of mycobacteria. Early steps of PIM synthesis are performed by the cytoplasmic enzymes PimA (Korduláková et al., 2002  ), PimB (Guerin et al., 2009; Lea-Smith et al., 2008) and PatA (Korduláková et al., 2003) to produce AcPIM2 from phosphatidylinositol (PI). Further mannosylation yields AcPIM4, which is transported to the periplasm and can be processed by the mannosyltransferase PimE (Morita et al., 2006) to form AcPIM6, an end product, or channelled into a parallel pathway for LM and LAM synthesis by the lipoprotein LpqW (Crellin et al., 2008; Kovacevic et al., 2006; Marland et al., 2006). LM/LAM synthesis is catalysed by the PPM-dependent mannosyltransferases MptB, MptA and MptC (Kaur et al., 2006, 2007; Mishra et al., 2007, 2008; Mishra, Krumbach et al., 2011). A phospholipid-binding protein, LmeA (Rahlwes et al., 2017), is involved in maintaining MptA under stress conditions (Rahlwes et al., 2020). The focus of the current study, LmcA (underlined), also functions at the MptA step in C. glutamicum (Cashmore et al., 2017). (b) The MSMEG_0317 genetic locus. The MSMEG_0317 gene is encoded within a locus that is highly conserved in Corynebacterineae. Likely orthologous genes in the three species are shown using the same colour. Previously studied genes are tmaT (Yamaryo-Botte et al., 2015) and mtrP (Rainczuk et al., 2020), both with roles in cell-wall mycolic acid transport, and the LM/LAM biosynthesis gene NCgl2760 (Cashmore et al., 2017), while the remaining genes are uncharacterized. The focus of the current study is boxed. (c) Predicted membrane topology of MSMEG_0317. Following cleavage of the putative signal peptide (red), the mature protein is proposed to comprise a large periplasmic N-terminal domain, a single transmembrane domain and a small cytoplasmic tail. (d) The elution profile of MSMEG_0317Δ on a HiLoad 16/60 Superdex 75 gel-filtration column suggesting a monomeric protein (top) and SDS–PAGE analysis of the eluted MSMEG_0317Δ (∼34 kDa) (bottom). The molecular-weight markers used for calibration are bovine γ-globulin (158 kDa), chicken ovalbumin (44 kDa) and equine myoglobin (17 kDa). See also Supplementary Fig. S1. |
![[Figure 1]](jb5039fig1.jpg)
 | STRUCTURAL BIOLOGY |
ISSN: 2059-7983
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