title: QueF-Like, a Non-Homologous Archaeosine Synthase from the Crenarchaeota.
abstract: Archaeosine (G⁺) is a structurally complex modified nucleoside ubiquitous to the Archaea, where it is found in the D-loop of virtually all archaeal transfer RNA (tRNA). Its unique structure, which includes a formamidine group that carries a formal positive charge, and location in the tRNA, led to the proposal that it serves a key role in stabilizing tRNA structure. Although G⁺ is limited to the Archaea, it is structurally related to the bacterial modified nucleoside queuosine, and the two share homologous enzymes for the early steps of their biosynthesis. In the Euryarchaeota, the last step of the archaeosine biosynthetic pathway involves the amidation of a nitrile group on an archaeosine precursor to give formamidine, a reaction catalyzed by the enzyme Archaeosine Synthase (ArcS). Most Crenarchaeota lack ArcS, but possess two proteins that inversely distribute with ArcS and each other, and are implicated in G⁺ biosynthesis. Here, we describe biochemical studies of one of these, the protein QueF-like (QueF-L) fromPyrobaculum calidifontis,that demonstrate the catalytic activity of QueF-L, establish where in the pathway QueF-L acts, and identify the source of ammonia in the reaction.
authors.affiliation: Department of Chemistry, Portland State University, Portland, OR 97207, USA. efectegerundi@gmail.com.
authors.forename: Adriana
authors.initials: A
authors.lastname: Bon Ramos
authors.affiliation: Department of Chemistry, Portland State University, Portland, OR 97207, USA. bold@imau.edu.cn.
authors.forename: Lide
authors.initials: L
authors.lastname: Bao
authors.affiliation: Department of Chemistry, Portland State University, Portland, OR 97207, USA. beturner@pdx.edu.
authors.forename: Ben
authors.initials: B
authors.lastname: Turner
authors.affiliation: The Department of Microbiology and Cell Science Department, University of Florida, Gainesville, FL 32611, USA. vcrecy@ufl.edu.
authors.forename: Valérie
authors.initials: V
authors.lastname: de Crécy-Lagard
authors.affiliation: Department of Chemistry, Portland State University, Portland, OR 97207, USA. iwatard@pdx.edu.
authors.forename: Dirk
authors.initials: D
authors.lastname: Iwata-Reuyl
mesh_terms: D055162:Biocatalysis; D006151:Guanosine / Q000031:analogs & derivatives* / Q000378:metabolism; D008025:Ligases / Q000235:genetics / Q000378:metabolism*; D041543:Pyrobaculum / Q000201:enzymology*
chemical_list: D006151:Guanosine; C081066:archaeosine; D008025:Ligases
keywords: amidinotransferase; archaeosine; biosynthesis; modified nucleoside; tunneling-fold superfamily