| Autor: |
Phillips G; Department of Microbiology, University of Florida, Gainesville, Florida 32611-0700, USA., Chikwana VM, Maxwell A, El-Yacoubi B, Swairjo MA, Iwata-Reuyl D, de Crécy-Lagard V |
| Jazyk: |
angličtina |
| Zdroj: |
The Journal of biological chemistry [J Biol Chem] 2010 Apr 23; Vol. 285 (17), pp. 12706-13. Date of Electronic Publication: 2010 Feb 03. |
| DOI: |
10.1074/jbc.M110.102236 |
| Abstrakt: |
The presence of the 7-deazaguanosine derivative archaeosine (G(+)) at position 15 in tRNA is one of the diagnostic molecular characteristics of the Archaea. The biosynthesis of this modified nucleoside is especially complex, involving the initial production of 7-cyano-7-deazaguanine (preQ(0)), an advanced precursor that is produced in a tRNA-independent portion of the biosynthesis, followed by its insertion into the tRNA by the enzyme tRNA-guanine transglycosylase (arcTGT), which replaces the target guanine base yielding preQ(0)-tRNA. The enzymes responsible for the biosynthesis of preQ(0) were recently identified, but the enzyme(s) catalyzing the conversion of preQ(0)-tRNA to G(+)-tRNA have remained elusive. Using a comparative genomics approach, we identified a protein family implicated in the late stages of archaeosine biosynthesis. Notably, this family is a paralog of arcTGT and is generally annotated as TgtA2. Structure-based alignments comparing arcTGT and TgtA2 reveal that TgtA2 lacks key arcTGT catalytic residues and contains an additional module. We constructed a Haloferax volcanii DeltatgtA2 derivative and demonstrated that tRNA from this strain lacks G(+) and instead accumulates preQ(0). We also cloned the corresponding gene from Methanocaldococcus jannaschii (mj1022) and characterized the purified recombinant enzyme. Recombinant MjTgtA2 was shown to convert preQ(0)-tRNA to G(+)-tRNA using several nitrogen sources and to do so in an ATP-independent process. This is the only example of the conversion of a nitrile to a formamidine known in biology and represents a new class of amidinotransferase chemistry. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
|
