National Institute of General Medical Sciences (1RC2GM092602–01 subcontract to V.d.C.-L.), the National Science Foundation (CHE0910751 to P.A.L.), and NASA (NNX07AJ26G to D. I.-R.).
Archaebacteria -- Molecular aspects, Archaebacteria -- Genetic aspects, Comparative genomics
Archaeosine (G+) is found at position 15 of many archaeal tRNAs. In Euryarchaeota, the G+ precursor, 7-cyano-7-deazaguanine (preQ0), is inserted into tRNA by tRNA-guanine transglycosylase (arcTGT) before conversion into G+ by ARChaeosine Synthase (ArcS). However, many Crenarchaeota known to harbor G+ lack ArcS homologs. Using comparative genomics approaches, two families that could functionally replace ArcS in these organisms were identified: 1) GAT-QueC, a two-domain family with an N-terminal glutamine amidotransferase class-II domain fused to a domain homologous to QueC, the enzyme that produces preQ0; 2) QueF-like, a family homologous to the bacterial enzyme catalyzing the reduction of preQ0 to 7- aminomethyl-7-deazaguanine. Here we show that these two protein families are able to catalyze the formation of G+ in a heterologous system. Structure and sequence comparisons of crenarchaeal and euryarchaeal arcTGTs suggest the crenarchaeal enzymes have broader substrate specificity. These results led to a new model for the synthesis and salvage of G+ in Crenarchaeota.
Phillips, Gabriela; Swairjo, Manal A.; Gaston, Kirk W.; Bailly, Marc; Limbach, Patrick A.; Iwata-Reuyl, Dirk; and de Crécy-Lagard, Valérie, "Diversity of Archaeosine Synthesis in Crenarchaeota" (2012). Chemistry Faculty Publications and Presentations. 92.