Hyperglycosylation of glycopeptidolipid of Mycobacterium smegmatis under nutrient starvation:: structural studies

The presence of a polar species of glycopepticlolipid (GPL) in carbon-starved Mycobacterium smegmatis has been reported previously. In this study, the complete structure of this GPL is established with the help of MALDI-TOF (matrix assisted laser desorption/ionization time of flight) and ESI (electrospray ionization) -MS, C-13-SEFT (spin echo Fourier transform) -MVR spectroscopy, and HPLC analysis. In the molecule, two units of a 3,4-di-O-methyl derivative of rhamnose are attached to L-alaninol via a 1 -> 2 linkage. Various methyl derivatives of rhamnose and 6-deoxytalose were synthesized as standards to establish this structure. The accumulation of this polar GPL in M. smegmatis is sigB dependent, as a SigB-overproducing strain of M. smegmatis shows the presence of this spot in the exponential phase, and a sigB-knockout strain of M. smegmatis does not show the presence of any polar GPLs.