02774nas a2200361   4500000000100000008004100001260001600042653002300058653002200081653002000103653001100123653003300134653003600167653002300203653001300226653002800239653003100267653001800298653006800316100001200384700001300396700001900409700001400428700001200442700001300454700002100467700001300488245017200501300001200673490000800685520170500693022001402398       2008                            d  c2008 Jan 1810aBacterial Proteins10aEnzyme Activation10aEpoxy Compounds10aEsters10aGenetic Complementation Test10aMagnetic Resonance Spectroscopy10aMethyltransferases10aMutation10aMycobacterium smegmatis10aMycobacterium tuberculosis10aMycolic Acids10aSpectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization1 aLaval F1 aHaites R1 aMovahedzadeh F1 aLemassu A1 aWong CY1 aStoker N1 aBillman-Jacobe H1 aDaffé M00aInvestigating the function of the putative mycolic acid methyltransferase UmaA: divergence between the Mycobacterium smegmatis and Mycobacterium tuberculosis proteins.  a1419-270 v2833 a<p>Mycolic acids are major and specific lipid components of the cell envelope of mycobacteria that include the causative agents of tuberculosis and leprosy, Mycobacterium tuberculosis and Mycobacterium leprae, respectively. Subtle structural variations that are known to be crucial for both their virulence and the permeability of their cell envelope occur in mycolic acids. Among these are the introduction of cyclopropyl groups and methyl branches by mycolic acid S-adenosylmethionine-dependent methyltransferases (MA-MTs). While the functions of seven of the M. tuberculosis MA-MTs have been either established or strongly presumed nothing is known of the roles of the remaining umaA gene product and those of M. smegmatis MA-MTs. Mutants of the M. tuberculosis umaA gene and its putative M. smegmatis orthologue, MSMEG0913, were created. The lipid extracts of the resulting mutants were analyzed in detail using a combination of analytical techniques such as matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and proton nuclear magnetic resonance spectroscopy, and chemical degradation methods. The M. smegmatis mutants no longer synthesized subtypes of mycolates containing a methyl branch adjacent to either trans cyclopropyl group or trans double bond at the "proximal" position of both alpha- and epoxy-mycolates. Complementation with MSMEG0913, but not with umaA, fully restored the wild-type phenotype in M. smegmatis. Consistently, no modification was observed in the structures of mycolic acids produced by the M. tuberculosis umaA mutant. These data proved that despite their synteny and high similarity umaA and MSMEG0913 are not functionally orthologous.</p>  a0021-9258