TCDB is operated by the Saier Lab Bioinformatics Group
TCIDNameDomainKingdom/PhylumProtein(s)
4.D.3.1.1









The glycan biosynthetic glucosyl transferase, OpgH (MdoH) of 847 aas and 6 - 9 TMSs.

Bacteria
Proteobacteria
OpgH of E. coli
4.D.3.1.2









Cellulose synthase of 516 aas and 6 - 8 TMSs. 

Archaea
Euryarchaeota
Cellulose synthase of Methanoculleus bourgensis (Methanogenium bourgense)
4.D.3.1.3









Glycosyl transferase group 2 family of 523 aas and 7 TMSs.

Bacteria
Tenericutes
Glycosyl transferase of Mycoplasma bovis
4.D.3.1.4









Trimeric cellulose synthase coomplex for primary cell wall synthesis, CESA1, 3 and 6 (Watanabe et al. 2015).  CESA1 is of 1084 aas and 8 TMSs while other CESA subunits are of similar size.  All three are catalytic subunit of the cellulose synthase complex. Required for beta-1,4-glucan microfibril crystallization, a major mechanism of primary cell wall formation. Required during embryogenesis for cell elongation, orientation of cell expansion and complex cell wall formation (Bashline et al. 2014). 
determined the structure of a poplar cellulose synthase CesA homotrimer that suggests a molecular basis for cellulose microfibril formation. This complex, stabilized by cytosolic plant-conserved regions and helical exchange within the transmembrane segments, forms three channels occupied by nascent cellulose polymers. Secretion steers the polymers toward a common exit point, which could facilitate protofibril formation. CesA's N-terminal domains assemble into a cytosolic stalk that interacts with a microtubule-tethering protein and may thus be involved in CesA localization.

Eukaryota
Viridiplantae
Cellulose synthase complex of Arabidopsis thaliana (Mouse-ear cress)
4.D.3.1.5









Cellulose synthase and transporter, BcsA, which functions with BcsB (periplasmic protein with an N-terminal TMS) and BcsC (an 18 β-stranded outer membrane porin). The x-ray structure of the BcsA-B complex has been determined at 3.5 Å resolution (Morgan et al. 2013).  Cellulose is synthesized and secreted by the membrane-integrated cellulose synthase.  Substrate- and product-bound structures of BcsA provided the basis for substrate recognition and demonstrated the stepwise elongation of cellulose. Structural snapshots showed that BcsA translocates cellulose via a ratcheting mechanism involving a 'finger helix' that contacts the polymer's terminal glucose. Cooperating with BcsA's gating loop, the finger helix moves 'up' and 'down' in response to substrate binding and polymer elongation, respectively, thereby pushing the elongated polymer into BcsA's transmembrane channel. This mechanism was validated by tethering BcsA's finger helix, which inhibits polymer translocation but not elongation (Morgan et al. 2016).

Bacteria
Proteobacteria
BcsA of Rhodobacter spheroides
4.D.3.1.6









Core cellulose synthase complex, BcsA/BcsB (Morgan et al. 2013; Omadjela et al. 2013).  BcsA (YhjO) is an 10 - 12 TMS protein with 4 N-terminal TMSs, the glycosyl transferase domain and 4 C-terminal TMSs.  It is believed to both synthesize the glycosyl linkages and transport the polysaccharide across the membrane (Römling and Galperin 2015).  BcsB (YhjN) is a cellulose synthase regulator, a cyclic diGMP binding protein, with two TMSs at the N- and C-termini and the bulk of the protein in the periplasm.  BcsC (TC# 1.B.55.3.1) is the outer membrane porin for the export of cellulose with an N-terminal α-TMS, a large N-terminal hydrophylic domain, and a C-terminal β-barrel domain.  Two other proteins, an endoglucanase, BscZ or YhjM, and a diguanylate cyclase, YedQ (TC# 9.B.34.1.4) may play roles in cellulose biosynthesis (Imai et al. 2014).  Cellulose is a component of the bacterial extracellular matrix (Zogaj et al. 2001) and plays roles in biofilm formation and cell adhesion (Hu et al. 2015).

Bacteria
Proteobacteria
BcsAB of E. coli
4.D.3.1.7









Cellulose synthase complex for secondary cell wall synthesis including CESA1, 3 and 6, all catalytic subunits (see 4.D.3.1.4) (Watanabe et al. 2015). A homolog (83% identical to Q8LPK5) from Populus tomentosa (Chinese white poplar) (CesA8) alone secretes the nascent polymer through a channel formed by its own transmembrane domain dependent on a lipid bilayer and Mn2+ to form microfibrils in vitro (Purushotham et al. 2016).

Eukaryota
Viridiplantae
Cellulose synthase complex of Arabidopsis thaliana
4.D.3.1.8









Cellulose synthase-like protein of 952 aas and about 7 TMSs, 3 (or 4) N-terminal and 6 C-terminal.  May catalyze both beta-1,3 and beta-1,4 glycosidic linkages in beta-D-glucan. Essential for (1,3;1,4)-beta-D-glucans synthesis in grasses and cereals (Poaceae). The mixed-linked glucans (which are not present in walls of dicotyledons or most other monocotyledonous plants) are particularly important constituents of the walls of the starchy endosperm and aleurone cells of cereal grains such as oats, wheat, rice and barley. They can account for up to 70% by weight of the wall.  A  single amino acid within the predicted transmembrane pore domain of CslF6 controls (1-3,1-4)-beta-glucan structure.  The membrane pore architecture and the translocation of the growing polysaccharide across the membrane control how the acceptor glucan is coordinated at the active site and thus the proportion of beta1-3 and beta1-4 bonds within the polysaccharide (Jobling 2015).  Residues involved in catalyses and flexibility have been identified (Dimitroff et al. 2016).  These influence theration of 1,3 to 1,4 linkages.

Eukaryota
Viridiplantae
CslF6 of Oryza sativa subsp. japonica (Rice)
4.D.3.1.9









Cellulose synthase-like protein D2, CslD2, of 1145 aas and 8 TMSs in at 2 (N-terminal) plus 6 (C-terminal) arrangement.

Eukaryota
Viridiplantae
CslD2 of Arabidopsis thaliana
4.D.3.1.10









Putative integral membrane glycosyl transferase, GT, of 451 aas and 4 TMSs.

Eukaryota
Viridiplantae
GT of Chlamydomonas reinhardtii (Chlamydomonas smithii)
4.D.3.1.11









Putative polysaccharide synthase and transporter, NdvB, essential for normal biofilm formation (Zhang and Mah 2008).

Bacteria
Proteobacteria
NdvB of Pseudomonas aeruginosa
4.D.3.1.12









Cellulose synthase 2, bcsABII-A of 1518 aas and 10 TMSs.

Bacteria
Proteobacteria
bcsABII-A of Komagataeibacter xylinus (Gluconacetobacter xylinus)
4.D.3.1.13









Cellulose synthase catalytic subunit (UDP-forming) of 1550 aas and 10 TMSs.

Bacteria
Proteobacteria
Cellulose synthase of Komagataeibacter europaeus
4.D.3.1.14









Cellulose synthase, CesA7, of 1042 aas and 8 TMSs in a 2 +3 + 3 TMS arrangement where the first two TMSs are in the first half of the protein while the last 6 are C-terminal. The cryo-EM structure of the homotrimeric CesA7 from Gossypium hirsutum has been reported at 3.5 Å resolution (Zhang et al. 2021). The GhCesA7 homotrimer shows a C3 symmetrical assembly. Each protomer contains seven transmembrane helices (TMSs) which form a channel potentially facilitating the release of newly synthesized glucans. The cytoplasmic glycosyltransferase domain (GT domain) of GhCesA7 protrudes from the membrane, and its catalytic pocket is directed towards the TM pore. The homotrimer GhCesA7 is stabilized by transmembrane helix 7 (TMS 7) and the plant conserved region (PCR) domains. It represents the building block of CSCs and facilitates microfibril formation. This structure provides insight into how eukaryotic cellulose synthase assembles (Zhang et al. 2021).

Eukaryota
Viridiplantae
Cellulose synthase, CesA7, of Gossypium hirsutum (Upland cotton) (Gossypium mexicanum)
4.D.3.2.1









Putative glycosyl transferase of 875 aas and 7 TMSs.

Eukaryota
Fungi
UP of Sclerotinia sclerotiorum