MF7000908 H49N mutant dTDP-4-keto-6-deoxy-D-glucose-3,4-ketoisomerase with TDP (Aneurinibacillus thermoaerophilus) 2pae X-ray 2.50 Homodimer Aneurinibacillus thermoaerophilus 17459872 Davis ML, Thoden JB, Holden HM J. Biol. Chem. 2007 26 282 19227-36 The repeating unit of the glycan chain in the S-layer of the bacterium Aneurinibacillus thermoaerophilus L420-91(T) is composed of four alpha-d-rhamnose molecules and two 3-acetamido-3,6-dideoxy-alpha-d-galactose moieties (abbreviated as Fucp3NAc). Formation of the glycan layer requires nucleotide-activated sugars as the donor molecules. Whereas the enzymes involved in the synthesis of GDP-rhamnose have been well characterized, less is known regarding the structures and enzymatic mechanisms of the enzymes required for the production of dTDP-Fucp3NAc. One of the enzymes involved in the biosynthesis of dTDP-Fucp3NAc is a 3,4-ketoisomerase, hereafter referred to as FdtA. Here we describe the first three-dimensional structure of this sugar isomerase complexed with dTDP and solved to 1.5 A resolution. The FdtA dimer assumes an almost jellyfish-like appearance with the sole alpha-helices representing the tentacles. Formation of the FdtA dimer represents a classical example of domain swapping whereby beta-strands 2 and 3 from one subunit form part of a beta-sheet in the second subunit. The active site architecture of FdtA is characterized by a cluster of three histidine residues, two of which, His(49) and His(51), appear to be strictly conserved in the amino acid sequences deposited to date. Site-directed mutagenesis experiments, enzymatic assays, and x-ray crystallographic analyses suggest that His(49) functions as an active site base. GO:0016853 isomerase activity 2 1 Homooligomeric enzymes Homodimeric enzymes All chains according to the most probable oligomerization state stored in PDBe were considered. A TDP-4-oxo-6-deoxy-alpha-D-glucose-3,4-oxoisomerase Aneurinibacillus thermoaerophilus Q6T1W8 1 136 97% MENKVINFKKIIDSRGSLVAIEENKNIPFSIKRVYYIFDTKGEEPRGFHAHKKLEQVLVCLNGSCRVILDDGNIIQEITLDSPAVGLYVGPAVWHEMHDFSSDCVMMVLASDYYDETDYIRQYDNFKKYIAKINLEKEG 139 secondary structure helix 117 119 secondary structure helix 124 138 secondary structure strand 7 9 secondary structure strand 12 15 secondary structure strand 18 24 secondary structure strand 35 40 secondary structure strand 48 53 secondary structure strand 58 64 secondary structure strand 67 72 secondary structure strand 77 82 secondary structure strand 87 91 secondary structure strand 96 100 secondary structure strand 107 112 secondary structure strand 121 122 pfam PF05523 WxcM-like, C-terminal 1 130 B TDP-4-oxo-6-deoxy-alpha-D-glucose-3,4-oxoisomerase Aneurinibacillus thermoaerophilus Q6T1W8 2 135 96% MENKVINFKKIIDSRGSLVAIEENKNIPFSIKRVYYIFDTKGEEPRGFHAHKKLEQVLVCLNGSCRVILDDGNIIQEITLDSPAVGLYVGPAVWHEMHDFSSDCVMMVLASDYYDETDYIRQYDNFKKYIAKINLEKEG 139 secondary structure helix 117 119 secondary structure helix 124 137 secondary structure strand 7 9 secondary structure strand 12 15 secondary structure strand 18 24 secondary structure strand 35 40 secondary structure strand 48 53 secondary structure strand 58 64 secondary structure strand 67 72 secondary structure strand 77 82 secondary structure strand 87 91 secondary structure strand 96 100 secondary structure strand 107 112 secondary structure strand 121 122 pfam PF05523 WxcM-like, C-terminal 1 130 Insufficient evidence (candidate) The full structure participates in mutual synergistic folding. WxcM-like, C-terminal Domain-swapped dimer with extensive subunit-subunit interface mainly contributed by beta sheet augmentation (PMID:17459872). A N/A B N/A MF7000908 MF7000909 MF7000910 MF7000911