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{{Infobox enzyme
| Name = S-adenosylmethionine:tRNA ribosyltransferase-isomerase
| EC_number = 2.4.99.17
| CAS_number = 
| IUBMB_EC_number = 2/4/99/17
| GO_code = 
| image = 
| width = 
| caption =
}}
'''S-adenosylmethionine:tRNA ribosyltransferase-isomerase''' ({{EC number|2.4.99.17}}, ''QueA enzyme'', ''queuosine biosynthesis protein QueA'') is an [[enzyme]] with system name ''S-adenosyl-L-methionine:7-aminomethyl-7-deazaguanosine ribosyltransferase (ribosyl isomerizing; L-methionine, adenine releasing)''.<ref>{{cite journal | title = A new function of ''S''-adenosylmethionine: the ribosyl moiety of AdoMet is the precursor of the cyclopentenediol moiety of the tRNA wobble base queuine |author = Slany, R.K., Bosl, M., Crain, P.F. and Kersten, H. |journal = Biochemistry |year = 1993 |volume = 32 |pages = 7811–7817 |pmid = 8347586 | doi = 10.1021/bi00081a028 | issue = 30}}</ref><ref>{{cite journal | title = Transfer and isomerization of the ribose moiety of AdoMet during the biosynthesis of queuosine tRNAs, a new unique reaction catalyzed by the QueA protein from ''Escherichia coli'' |author = Slany, R.K., Bosl, M. and Kersten, H. |journal = Biochimie |year = 1994 |volume = 76 |pages = 389–393 |pmid = 7849103 | doi = 10.1016/0300-9084(94)90113-9 | issue = 5}}</ref><ref>{{cite journal | title = Mechanistic studies of the tRNA-modifying enzyme QueA: a chemical imperative for the use of AdoMet as a "ribosyl" donor |author = Kinzie, S.D., Thern, B. and Iwata-Reuyl, D. |journal = Org. Lett. |year = 2000 |volume = 2 |pages = 1307–1310 |pmid = 10810734 | doi = 10.1021/ol005756h | issue = 9}}</ref><ref>{{cite journal | title = Kinetic mechanism of the tRNA-modifying enzyme ''S''-adenosylmethionine:tRNA ribosyltransferase-isomerase (QueA) |author = Van Lanen, S.G. and Iwata-Reuyl, D. |journal = Biochemistry |year = 2003 |volume = 42 |pages = 5312–5320 |pmid = 12731872 | doi = 10.1021/bi034197u | issue = 18}}</ref><ref>{{cite journal | title = Crystal structure of ''S''-adenosylmethionine:tRNA ribosyltransferase-isomerase (QueA) from ''Thermotoga maritima'' at 2.0 &Aring; resolution reveals a new fold |author = Mathews, I., Schwarzenbacher, R., McMullan, D., Abdubek, P., Ambing, E., Axelrod, H., Biorac, T., Canaves, J.M., Chiu, H.J., Deacon, A.M., DiDonato, M., Elsliger, M.A., Godzik, A., Grittini, C., Grzechnik, S.K., Hale, J., Hampton, E., Han, G.W., Haugen, J., Hornsby, M., Jaroszewski, L., Klock, H.E., Koesema, E., Kreusch, A., Kuhn, P., Lesley, S.A., Levin, I., Miller, M.D., Moy, K., Nigoghossian, E., Ouyang, J., Paulsen, J., Quijano, K., Reyes, R., Spraggon, G., Stevens, R.C., van den Bedem, H., Velasquez, J., Vincent, J., White, A., Wolf, G., Xu, Q., Hodgson, K.O., Wooley, J. and Wilson, I.A. |journal = Proteins |year = 2005 |volume = 59 |pages = 869–874 |pmid = 15822125 | doi = 10.1002/prot.20419 | issue = 4}}</ref><ref>{{cite journal | title = Crystal structure of ''Bacillus subtilis'' ''S''-adenosylmethionine:tRNA ribosyltransferase-isomerase |author = Grimm, C., Ficner, R., Sgraja, T., Haebel, P., Klebe, G. and Reuter, K. |journal = Biochem. Biophys. Res. Commun. |year = 2006 |volume = 351 |pages = 695–701 |pmid = 17083917 | doi = 10.1016/j.bbrc.2006.10.096 | issue = 3}}</ref> This enzyme [[catalysis|catalyses]] the following [[chemical reaction]]

: [[S-adenosyl-L-methionine]] + 7-aminomethyl-7-carbaguanosine<sup>34</sup> in tRNA <math>\rightleftharpoons</math> L-[[methionine]] + [[adenine]] + epoxyqueuosine<sup>34</sup> in tRNA

The reaction is a combined transfer and [[isomerization]] of the [[ribose]] moiety of S-adenosyl-L-methionine to the modified [[guanosine]] base in the wobble position in tRNAs specific for Tyr, His, Asp or Asn.

== References ==
{{reflist}}

== External links ==
*{{MeshName|S-adenosylmethionine:tRNA+ribosyltransferase-isomerase}}

[[Category:EC 2.4.99]]