Sequencing of Oligoarabinosyl Units Released from Mycobacterial Arabinogalactan by Endogenous Arabinanase: Identification of Distinctive and Novel Structural Motifs

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• 作者：Arwen Lee ; Sz-Wei Wu ; Michael S. Scherman ; Jordi B. Torrelles ; Delphi Chatterjee ; Michael R. McNeil ; Kay-Hooi Khoo
• 刊名：Biochemistry
• 出版年：2006
• 出版时间：December 26, 2006
• 年：2006
• 卷：45
• 期：51
• 页码：15817 - 15828
• 全文大小：1001K
• 年卷期：v.45,no.51(December 26, 2006)
• ISSN：1520-4995

文摘

The mycobacterial D-arabinofuran is a common constituent of both cell wall mycolyl-arabinogalactan (AG) and the associated lipoarabinomannan (LAM), and is thus accorded critical structuraland immunological roles. Despite a well-recognized importance, progress in understanding its full structuralcharacteristics beyond the nonreducing terminal motifs has hitherto been limited by available analyticaltools. An endogenous arabinanase activity recently isolated from Mycobacterium smegmatis was previouslyshown to be capable of releasing large oligoarabinosyl units from AG. Advanced tandem mass spectrometryutilizing both low and high energy collision induced dissociation now afforded a facile way to map anddirectly sequence the digestion products which were dominated by distinctive Ara₁₈ and Ara₁₉ structuralunits, together with Ara₇ and lesser amount of Ara₁₁ and Ara₁₂. Significantly, evidence was obtained forthe first time which validated the linkages and branching pattern of the previously inferred Ara₂₂ structuralmotif of AG, on which the preferred cleavage sites of the novel arabinanase could be localized. Theestablished linkage-specific MS/MS fragmentation characteristics further led to identification of agalactosamine substituent on the C2 position of a portion of the internal 3,5-branched Ara residue of theAG of Mycobacterium tuberculosis, but not that of the nonpathogenic, fast growing M. smegmatis.