1887

Abstract

The Emb proteins (EmbA, EmbB, EmbC) are mycobacterial arabinosyltransferases involved in the biogenesis of the mycobacterial cell wall. EmbA and EmbB are predicted to work in unison as a heterodimer. EmbA and EmbB are involved in the formation of the crucial terminal hexaarabinoside motif [Ara(1→2)Ara(1→5)] [Ara(1→2)Ara(1→3)]Ara(1→5)Ara1→(Ara) in the cell wall polysaccharide arabinogalactan. Studies conducted in revealed that mutants with disruptions in or are viable, although the growth rate was affected. In contrast, we demonstrate here that is an essential gene in , since a deletion of the chromosomal gene could only be achieved when a second functional copy was provided on an integrated vector. Complementation of an mutant of by confirmed that it encodes a functional arabinosyltransferase. We identified a promoter for located immediately upstream of the gene, indicating that it is expressed independently from the upstream gene, . Promoter activity from P was sevenfold lower when assayed in compared to , indicating that the latter is not a good host for genetic analysis of expression. P activity remained constant throughout growth phases and after stress treatment, although it was reduced during hypoxia-induced non-replicating persistence. Ethambutol exposure had no effect on P activity. These data demonstrate that encodes a functional arabinosyltransferase which is constitutively expressed and plays a critical role in .

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2008-01-01
2024-03-28
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