Structural insights into terminal arabinosylation of mycobacterial cell wall arabinan
The global challenge of tuberculosis, caused by Mycobacterium tuberculosis (Mtb), is compounded by the emergence of drug-resistant strains. A critical factor in Mtb's pathogenicity is its intricate cell envelope, which acts as a formidable barrier against immune defences and pharmacological interventions. Central to this envelope are arabinogalactan (AG) and lipoarabinomannan (LAM), two complex polysaccharides containing arabinan domains essential for maintaining cell wall structure and function. The arabinofuranosyltransferase AftB plays a pivotal role in the biosynthesis of these arabinan domains by catalyzing the addition of β-(1 → 2)-linked terminal arabinofuranose residues. Here, we present the cryo-EM structures of Mycobacterium chubuense AftB in both its apo form and bound to a donor substrate analog, resolved at 2.9 Å and 3.4 Å resolution, respectively. These structures reveal that AftB has a GT-C fold, with a transmembrane (TM) domain comprised of eleven TM helices and a periplasmic cap domain. AftB has a distinctive irregular, tube-shaped cavity that connects two proposed substrate binding sites. Through an integrated approach combining structural analysis, biochemical assays, and molecular dynamics simulations, we delineate the molecular basis of AftB's reaction mechanism and propose a model for its catalytic function.
Authors
- Todd L. Lowary (ORCID: https://orcid.org/0000-0002-8331-8211)
- Shih-Yun Guu (ORCID: https://orcid.org/0009-0007-1886-5140)
- Hung‐Yu Chen (ORCID: https://orcid.org/0000-0003-0253-3567)
- Filippo Mancia (ORCID: https://orcid.org/0000-0003-3293-2200)
- Po‐Sen Tseng (ORCID: https://orcid.org/0000-0003-2860-5725)
- Rie Nygaard (ORCID: https://orcid.org/0000-0002-0425-234X)
- Satchal K. Erramilli (ORCID: https://orcid.org/0000-0001-8694-7681)
- Margarida Archer (ORCID: https://orcid.org/0000-0001-8419-5420)
- Brian Kloss (ORCID: https://orcid.org/0000-0003-0130-8739)
- Phillip J. Stansfeld (ORCID: https://orcid.org/0000-0001-8800-7669)
- José Rodrigues (ORCID: https://orcid.org/0000-0003-0829-9054)
- Yaqi Liu (ORCID: https://orcid.org/0009-0008-3066-797X)
- Chelsea M. Brown (ORCID: https://orcid.org/0000-0003-2006-5015)
- Anthony A. Kossiakoff (ORCID: https://orcid.org/0000-0003-3174-9359)
- Piotr Tokarz (ORCID: https://orcid.org/0000-0002-7618-7540)
- Kay‐Hooi Khoo (ORCID: https://orcid.org/0000-0003-2906-406X)
- Nam Ha Duong (ORCID: https://orcid.org/0009-0000-3626-6271)
- Yi‐Chia Su (ORCID: https://orcid.org/0000-0002-9544-1153)
- Yu-Jen Wang (ORCID: https://orcid.org/0000-0003-1229-3368)
- Cheng-Ruei Han
Institutions
- University of Alberta (CA)
- National Taiwan University (TW)
- University of Groningen (NL)
- Cornell University (US)
- National Tsing Hua University (TW)
- Columbia University Irving Medical Center (US)
- University of Warwick (GB)
- University of Chicago (US)
- Institute of Biological Chemistry, Academia Sinica (TW)
- Universidade Nova de Lisboa (PT)
- Academia Sinica (TW)
Publication Details
- Journal
- Nature Communications
- Published
- 2025-04-29
- DOI
- https://doi.org/10.1038/s41467-025-58196-5
- Citations
- 3
- Primary Topic
- Glycosylation and Glycoproteins Research
- Type
- article
- Field-Weighted Citation Impact
- 2.42
Funders
- University of Warwick
- Academia Sinica
- National Institutes of Health
- Horizon 2020 Framework Programme
- Medical Research Council
- Engineering and Physical Sciences Research Council
- Biotechnology and Biological Sciences Research Council
- Fundação para a Ciência e a Tecnologia
- Canadian Glycomics Network
- National Institute of General Medical Sciences