title: 6-pyruvoyltetrahydropterin synthase paralogs replace the folate synthesis enzyme dihydroneopterin aldolase in diverse bacteria.
abstract: Dihydroneopterin aldolase (FolB) catalyzes conversion of dihydroneopterin to 6-hydroxymethyldihydropterin (HMDHP) in the classical folate biosynthesis pathway. However, folB genes are missing from the genomes of certain bacteria from the phyla Chloroflexi, Acidobacteria, Firmicutes, Planctomycetes, and Spirochaetes. Almost all of these folB-deficient genomes contain an unusual paralog of the tetrahydrobiopterin synthesis enzyme 6-pyruvoyltetrahydropterin synthase (PTPS) in which a glutamate residue replaces or accompanies the catalytic cysteine. A similar PTPS paralog from the malaria parasite Plasmodium falciparum is known to form HMDHP from dihydroneopterin triphosphate in vitro and has been proposed to provide a bypass to the FolB step in vivo. Bacterial genes encoding PTPS-like proteins with active-site glutamate, cysteine, or both residues were accordingly tested together with the P. falciparum gene for complementation of the Escherichia coli folB mutation. The P. falciparum sequence and bacterial sequences with glutamate or glutamate plus cysteine were active; those with cysteine alone were not. These results demonstrate that PTPS paralogs with an active-site glutamate (designated PTPS-III proteins) can functionally replace FolB in vivo. Recombinant bacterial PTPS-III proteins, like the P. falciparum enzyme, mediated conversion of dihydroneopterin triphosphate to HMDHP, but other PTPS proteins did not. Neither PTPS-III nor other PTPS proteins exhibited significant dihydroneopterin aldolase activity. Phylogenetic analysis indicated that PTPS-III proteins may have arisen independently in various PTPS lineages. Consistent with this possibility, merely introducing a glutamate residue into the active site of a PTPS protein conferred incipient activity in the growth complementation assay, and replacing glutamate with alanine in a PTPS-III protein abolished complementation.
authors.affiliation: Horticultural Sciences Department, University of Florida, Gainesville, Florida 32611, USA.
authors.forename: Anne
authors.initials: A
authors.lastname: Pribat
authors.forename: Linda
authors.initials: L
authors.lastname: Jeanguenin
authors.forename: Aurora
authors.initials: A
authors.lastname: Lara-Núñez
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Ziemak
authors.forename: John E
authors.initials: JE
authors.lastname: Hyde
authors.forename: Valérie
authors.initials: V
authors.lastname: de Crécy-Lagard
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Hanson
mesh_terms: D000446:Aldehyde-Lyases / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001419:Bacteria / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism*; D001708:Biopterins / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D019295:Computational Biology; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D005492:Folic Acid / Q000737:chemistry / Q000378:metabolism; D005816:Genetic Complementation Test; D005822:Genetic Vectors; D008954:Models, Biological; D008969:Molecular Sequence Data; D015394:Molecular Structure; D016297:Mutagenesis, Site-Directed; D019798:Neopterin / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism; D019761:Phosphorus-Oxygen Lyases / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid; D013763:Tetrahydrofolates / Q000737:chemistry / Q000378:metabolism
chemical_list: D029968:Escherichia coli Proteins; D013763:Tetrahydrofolates; C013490:dihydroneopterin triphosphate; D001708:Biopterins; C030371:5,6,7,8-tetrahydrofolic acid; D019798:Neopterin; D005492:Folic Acid; D000446:Aldehyde-Lyases; C020044:dihydroneopterin aldolase; D019761:Phosphorus-Oxygen Lyases; C043497:6-pyruvoyltetrahydropterin synthase; C003402:sapropterin