28461332, J Biol Chem. 2017 Jun 23;292(25):10639-10650. doi: 10.1074/jbc.M117.787606. Epub 2017 May 1.

Characterization method

RT-PCR,enzyme activity assay

Genomic accession number


Nucelotide position range







Bacteroides thetaiotaomicron/818

Degradation or Biosynthesis


Gene Name

Locus Tag

Protein ID

Gene Position

GenBank Contig Range

EC Number

- BT_3309 AAO78415.1 0 - 1644 (+) AE015928.1:4246707-4248351 -
- BT_3310 AAO78416.1 1853 - 4859 (+) AE015928.1:4248560-4251566 -
- BT_3311 AAO78417.1 4873 - 6394 (+) AE015928.1:4251580-4253101 -
- BT_3312 AAO78418.1 6452 - 7943 (+) AE015928.1:4253159-4254650 -
- BT_3313 AAO78419.1 7965 - 9969 (+) AE015928.1:4254672-4256676 -
- BT_3314 AAO78420.1 9986 - 12281 (+) AE015928.1:4256693-4258988 -

Cluster number


Gene name

Gene position

Gene type

Found by CGCFinder?

- 1 - 1644 (+) CDS No
- 1854 - 4859 (+) TC: gnl|TC-DB|Q45780|1.B.14.6.1 Yes
- 4874 - 6394 (+) other Yes
- 6453 - 7943 (+) CAZyme: GH30|GH30_3 Yes
- 7966 - 9969 (+) other Yes
- 9987 - 12281 (+) CAZyme: GH3 Yes




28461332, J Biol Chem. 2017 Jun 23;292(25):10639-10650. doi: 10.1074/jbc.M117.787606. Epub 2017 May 1.


A Bacteroidetes locus dedicated to fungal 1,6-beta-glucan degradation: Unique substrate conformation drives specificity of the key endo-1,6-beta-glucanase.


Temple MJ, Cuskin F, Basle A, Hickey N, Speciale G, Williams SJ, Gilbert HJ, Lowe EC


Glycans are major nutrients available to the human gut microbiota. The Bacteroides are generalist glycan degraders, and this function is mediated largely by polysaccharide utilization loci (PULs). The genomes of several Bacteroides species contain a PUL, PUL(1,6-beta-glucan), that was predicted to target mixed linked plant 1,3;1,4-beta-glucans. To test this hypothesis we characterized the proteins encoded by this locus in Bacteroides thetaiotaomicron, a member of the human gut microbiota. We show here that PUL(1,6-beta-glucan) does not orchestrate the degradation of a plant polysaccharide but targets a fungal cell wall glycan, 1,6-beta-glucan, which is a growth substrate for the bacterium. The locus is up-regulated by 1,6-beta-glucan and encodes two enzymes, a surface endo-1,6-beta-glucanase, BT3312, and a periplasmic beta-glucosidase that targets primarily 1,6-beta-glucans. The non-catalytic proteins encoded by PUL(1,6-beta-glucan) target 1,6-beta-glucans and comprise a surface glycan-binding protein and a SusD homologue that delivers glycans to the outer membrane transporter. We identified the central role of the endo-1,6-beta-glucanase in 1,6-beta-glucan depolymerization by deleting bt3312, which prevented the growth of B. thetaiotaomicron on 1,6-beta-glucan. The crystal structure of BT3312 in complex with beta-glucosyl-1,6-deoxynojirimycin revealed a TIM barrel catalytic domain that contains a deep substrate-binding cleft tailored to accommodate the hook-like structure adopted by 1,6-beta-glucan. Specificity is driven by the complementarity of the enzyme active site cleft and the conformation of the substrate. We also noted that PUL(1,6-beta-glucan) is syntenic to many PULs from other Bacteroidetes, suggesting that utilization of yeast and fungal cell wall 1,6-beta-glucans is a widespread adaptation within the human microbiota.