Transfer RNA tour: Difference between revisions

The <scene name='72/725890/Trna_u--turn/1'>conserved ''U-turn'' motifs</scene> are responsible for turns in the <B><FONT COLOR="#ff0000">anticodon</FONT></B> and <B><FONT COLOR="#008aff">T</FONT></B> loops. The turn is stabilized by an H-bond between a conserved U residue and the phosphate backbone and an H-bond fron the O2' of the U to the N7 of a conserved purine. <scene name='72/725890/Trna_u--turn/3'>Zoom in on the anticodon-loop U-turn</scene>. Residues <B><FONT COLOR="#ff0000">33-35</FONT></B> form the <B>U-turn</B>, N3 of <B><FONT COLOR="#ff0000">U33</FONT></B> H-bonds to the phosphate oxygen of <B><FONT COLOR="#ff00ff">A36</FONT></B>, the O2' of <B><FONT COLOR="#ff0000">U33</FONT></B> H-bonds to the N7 of <B><FONT COLOR="#ff0000">A35</FONT></B>. Residues <B><FONT COLOR="#ff0000">34</FONT></B>, <B><FONT COLOR="#ff0000">35</FONT></B> and <B><FONT COLOR="#ff00ff">36</FONT></B> are the anticodon bases used in translation. The hypermodified wybutrosine <B><FONT COLOR="#aaaa00">YG37</FONT></B> is believed to form a steric block to frameshifting during translation.

The ''U-turn'' motif is repeated in the <B><FONT COLOR="#008aff">&quot;T-loop&quot;</FONT></B> of tRNA. <scene name='72/725890/Trna_u--turn/4'>Zoom in on the T-loop U-turn</scene>. Residues <B><FONT COLOR="#008aff">55-57</FONT></B> form the U-turn here.  A <B>U-turn</B> is also found in the active site of the hammerhead ribozyme.