This entry represents the third domain of GlfT2 (Rv3808c), a polymerising galactofuranosyltransferase that synthesises the galactan portion of the peptidoglycan complex of the mycobacteria cell wall. It consists of eight alpha-helices, five of which immediately follow the glycosyltransferase (GT) domain and form the central portion of domain 3. Three helices at the C terminus of the polypeptide chain wrap around these core helices to complete the domain. The first helix in domain 3 anchors loop 1 and is conserved in many GT-A proteins. The flanking domains and many hydrophobic residues found at the interface between domains 2 and 3 of this protein are conserved among many proteins of mycobacteria, related Actinobacteria and more distantly related species, suggesting conserved structure structure and function relationships. The alpha2- and alpha6-helices from domain 3 and alpha1 from domain 4 contribute with a patch of exposed hydrophobic residues which probably generate a binding site for the hydrophobic acyl chains of membrane phospholipids. These surface-exposed hydrophobic residues may also contribute to the specificity and affinity binding of UDP donors [1].

1: Tetrameric structure of the GlfT2 galactofuranosyltransferase reveals a scaffold for the assembly of mycobacterial Arabinogalactan. Wheatley RW, Zheng RB, Richards MR, Lowary TL, Ng KK; J Biol Chem. 2012;287:28132-28143. PMID:22707726