De Sousa-D'Auria Célia, Kacem Raoudha, Puech Virginie, Tropis Marielle, Leblon Gérard, Houssin Christine, Daffé Mamadou
Laboratoire de Biotechnologie des Microorganismes d'Intérêt Industriel, Institut de Génétique et Microbiologie, UMR 8621 du CNRS et de l'Université Paris-Sud, 91405 Orsay, France.
FEMS Microbiol Lett. 2003 Jul 15;224(1):35-44. doi: 10.1016/S0378-1097(03)00396-3.
Mycolic acids, the major lipid constituents of Corynebacterineae, play an essential role in maintaining the integrity of the bacterial cell envelope. We have previously characterized a corynebacterial mycoloyltransferase (PS1) homologous in its N-terminal part to the three known mycobacterial mycoloyltransferases, the so-called fibronectin-binding proteins A, B and C. The genomes of Corynebacterium glutamicum (ATCC13032 and CGL2005) and Corynebacterium diphtheriae were explored for the occurrence of other putative corynebacterial mycoloyltransferase-encoding genes (cmyt). In addition to csp1 (renamed cmytA), five new cmyt genes (cmytB-F) were identified in the two strains of C. glutamicum and three cmyt genes in C. diphtheriae. In silico analysis showed that each of the putative cMyts contains the esterase domain, including the three key amino acids necessary for the catalysis. In C. glutamicum CGL2005 cmytE is a pseudogene. The four new cmyt genes were disrupted in this strain and overexpressed in the inactivated strains. Quantitative analyses of the mycolate content of all these mutants demonstrated that each of the new cMyt-defective strains, except cMytC, accumulated trehalose monocorynomycolate and exhibited a lower content of covalently bound corynomycolate than did the parent strain. For each mutant, the mycolate content was fully restored by complementation with the corresponding wild-type gene. Finally, complementation of the cmytA-inactivated mutant by the individual new cmyt genes established the existence of two classes of mycoloyltransferases in corynebacteria.
分枝菌酸是棒杆菌科的主要脂质成分，在维持细菌细胞壁完整性方面发挥着重要作用。我们之前鉴定了一种棒状杆菌分枝菌酰基转移酶（PS1），其N端部分与三种已知的分枝杆菌分枝菌酰基转移酶同源，即所谓的纤连蛋白结合蛋白A、B和C。我们对谷氨酸棒杆菌（ATCC13032和CGL2005）及白喉棒杆菌的基因组进行了探索，以寻找其他假定的棒状杆菌分枝菌酰基转移酶编码基因（cmyt）。除了csp1（重新命名为cmytA），在两株谷氨酸棒杆菌中鉴定出了五个新的cmyt基因（cmytB - F），在白喉棒杆菌中鉴定出了三个cmyt基因。计算机分析表明，每个假定的cMyts都包含酯酶结构域，包括催化所需的三个关键氨基酸。在谷氨酸棒杆菌CGL2005中，cmytE是一个假基因。这四个新的cmyt基因在该菌株中被破坏，并在失活菌株中过表达。对所有这些突变体的分枝菌酸含量进行定量分析表明，除了cMytC外，每个新的cMyt缺陷菌株都积累了海藻糖单棒状菌酸酯，并且与亲本菌株相比，共价结合的棒状菌酸含量较低。对于每个突变体，通过用相应的野生型基因进行互补，分枝菌酸含量完全恢复。最后，用单个新的cmyt基因对cmytA失活突变体进行互补，证实了棒状杆菌中存在两类分枝菌酰基转移酶。
