The arabinogalactan of Corynebacterianeae is a critical heteropolysaccharide that tethers outer membrane mycolic acids to peptidoglycan thus forming the characteristic cell wall core of these prokaryotes. An essential α-(1→5)-arabinosyltransferase, AftA, is responsible for the transfer of the first arabinofuranosyl (Araf) unit of the arabinan domain to the galactan backbone of arabinogalactan, but the number and precise position at which Araf residue(s) is/are added in mycobacteria remain ill-defined. Using membrane preparations from Mycobacterium smegmatis overexpressing aftA, farnesyl-phospho-arabinose as an Araf donor, and a series of synthetic galactan acceptors of various lengths, we here show that a single priming arabinosyl residue substitutes the C-5 position of a precisely positioned internal 6-linked galactofuranosyl residue of the galactan acceptors, irrespective of their length. This unexpected result suggests that, like the structurally related mycobacterial lipoarabinomannans, the arabinogalactan of mycobacteria may in fact harbor a single arabinan chain.

中文翻译：

---

使用合成糖脂探测分枝杆菌阿拉伯半乳聚糖上阿拉伯聚糖链的数量和位置


棒杆菌的阿拉伯半乳聚糖是一种关键的杂多糖，它将外膜分枝菌酸与肽聚糖连接，从而形成这些原核生物的特征性细胞壁核心。必需的 α-(1→5)-阿拉伯糖基转移酶 AftA 负责将阿拉伯聚糖结构域的第一个阿拉伯呋喃糖基 (Ara f ) 单元转移至阿拉伯半乳聚糖的半乳聚糖主链，但 Ara f残基的数量和精确位置(s) 是否添加到分枝杆菌中仍然不明确。使用来自过表达aftA的耻垢分枝杆菌的膜制剂、作为 Ara f供体的法呢基磷酸阿拉伯糖和一系列不同长度的合成半乳聚糖受体，我们在此表明​​，单个引发阿拉伯糖基残基取代了精确定位的 C-5 位置。半乳聚糖受体的内部 6-连接呋喃半乳糖残基，无论其长度如何。这一意想不到的结果表明，与结构相关的分枝杆菌脂阿拉伯甘露聚糖一样，分枝杆菌的阿拉伯半乳聚糖实际上可能含有单个阿拉伯聚糖链。