Characterization of a distinct arabinofuranosyltransferase in Mycobacterium smegmatis.

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Zhang J, Khoo KH, Wu SW, Chatterjee D

Characterization of a distinct arabinofuranosyltransferase in Mycobacterium smegmatis.

J Am Chem Soc. 2007 Aug 8;129(31):9650-62. Epub 2007 Jul 14.

PubMed ID

17630736 [ View in PubMed

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Abstract

The D-arabinans in Mycobacterium are essential, extraordinarily complex entity comprised of d-arabinofuranose residues which are rarely found in nature. Despite the well-recognized importance of the mycobacterial arabinan, delineation of the arabinosylation process has been severely hampered due to lack of positively identified arabinosyltransferases. Identification of genes involved in arabinan biosynthesis entailed the use of ethambutol (EMB), a first-line antituberculosis agent that is known to inhibit cell wall arabinan synthesis. The three genes (embA, embB, and embC) encode novel membrane proteins, implicated as the only known mycobacterial arabinosyltransferases to this date. We have now adapted a multifaceted approach involving development of convenient arabinosyltransferase assay using novel synthetic acceptors to identify arabinosyltransferase/s that will be distinct from the Emb proteins. In our present work, Mycobacterium smegmatis mc(2) 155 (WTMsm) was used as a model to study the biosynthesis of cell wall arabinan. In an in vitro assay, we demonstrate that transfer of only alpha-Araf had occurred from decaprenylphosphoryl-D-arabinofuranose (DPA) on a newly synthesized branched acceptor [alpha-D-Araf](2)-3,5-alpha-D-Araf-(1-->5)-alpha-d-Araf-(1-->5)-alpha-D-Araf with an octyl aglycon. Higher molecular weight (up to Ara(10)) oligomers were also detected in a parallel reaction using cold phosphoribosepyrophosphate (pRpp). Matrix-assisted laser desorption ionization time-of-flight tandem mass spectrometry (MALDI-TOF MS/MS) analysis of these products revealed that isomeric products were formed and initiation and elongation of arabinan can occur either on the 5-arm or 3-arm of the branched 3,5-alpha-D-Araf. Individual embA, embB, and embC knockout strains retained this alpha-1,5 arabinosyltransferase activity, and the activity was partially inhibited by ethambutol. This particular enzyme function is distinct from the function of the Emb proteins.

DrugBank Data that Cites this Article

Drug Targets

Drug	Target	Kind	Organism	Pharmacological Action	Actions
Ethambutol	Probable arabinosyltransferase A	Protein	Mycobacterium tuberculosis	Yes	Inhibitor	Details
Ethambutol	Probable arabinosyltransferase C	Protein	Mycobacterium tuberculosis	Yes	Inhibitor	Details