Protein Domain : ApbE-like superfamily IPR003374

Type	Homologous_superfamily
Description	This superfamily previously known as ApbE (thought to be involved in thiamine biosynthesis, alternatively known as Mg2+-dependent flavin transferase that has a role in catalysing the covalent attachment of FMN to a threonine residue in bacterial flavoproteins [ ]) was renamed to Ftp (flavin-trafficking protein) in 2013 due to the characterisation of TP0796, a lipoprotein from T. pallidum, which is classified as a putative member of the ApbE superfamily (). FAD pyrophosphatase () catalyses the hydrolysis of FAD, forming AMP and FMN. To date, the Ftp (TP0796) of T. pallidum is the first bacterial FAD pyrophosphatase shown to have a strict requirement for Mg2+ for its catalytic activity. Other Ftp homologs (formerly known as ApbE proteins) are present in the genomes of numerous bacteria and in lower eukaryotes, such as Trypanosoma spp. (agents of sleeping sickness and Chagas disease) and Leishmania spp. (agent of leishmaniasis), but the eukaryotic homologs appear to be fused with a multidomain fumarate reductase. Other members of the ApbE superfamily are related to the periplasmic ApbE lipoprotein of Salmonella typhimurium. In S. typhimurium, ApbE has been shown to be involved in thiamine biosynthesis and may serve in the conversion of aminoimidazole ribotide to 4-amino-5-hydroxymethyl-2-methylpyrimidine. T. pallidum is predicted to lack the thiamine pathway as well as the enzymes involved in aminoimidazole ribotide metabolism. The periplasmic location of ApbE prompts questions concerning how it could participate in a cytoplasmic pathway. ApbE proteins are relatively understudied biochemically, and representative crystal structures (PDB entries and ) have failed to definitively elucidate their functions. Some studies have shown that some of the Ftp family proteins bind FAD and that the Ftp protein from Vibrio harveyi transfers the FMN portion of FAD to a subunit of the integral inner membrane Nqr redox pump. The crystal structure of Ftp from T. pallidum displays a highly conserved Ftp fold and an active site/FAD-binding site of all known Ftp-like proteins.
Short Name	ApbE-like_sf