Editing Pyrrolysine (section)

==Potential for an alternative translation==
The tRNA(CUA) can be charged with [[lysine]] ''in vitro'' by the concerted action of the ''M. barkeri'' Class I and Class II lysyl-tRNA synthetases, which do not recognize pyrrolysine. Charging a tRNA(CUA) with lysine was originally hypothesized to be the first step in translating UAG amber [[codon]]s as pyrrolysine, a mechanism analogous to that used for [[selenocysteine]]. More recent data favor direct charging of pyrrolysine on to the tRNA(CUA) by the protein product of the ''pylS'' gene, leading to the suggestion that the LysRS1:LysRS2 complex may participate in a parallel pathway designed to ensure that proteins containing the UAG codon can be fully translated using lysine as a substitute amino acid in the event of pyrrolysine deficiency.<ref>{{cite journal|doi=10.1073/pnas.0405362101|pmc=515082|title=An aminoacyl-tRNA synthetase that specifically activates pyrrolysine|pmid=15314242|journal=Proceedings of the National Academy of Sciences of the United States of America|date=2004-08-24|volume=101|issue=34|pages=12450–12454|bibcode = 2004PNAS..10112450P |last1=Polycarpo|first1=C|last2=Ambrogelly|first2=A|last3=Bérubé|first3=A|last4=Winbush|first4=S. M.|last5=McCloskey|first5=J. A.|last6=Crain|first6=P. F.|last7=Wood|first7=J. L.|last8=Söll|first8=D|doi-access=free}}</ref> Further study found that the genes encoding LysRS1 and LysRS2 are not required for normal growth on [[methanol]] and methylamines with normal methyltransferase levels, and they cannot replace ''pylS'' in a recombinant system for UAG amber stop codon suppression.<ref>{{cite journal | pmid = 17542922 | doi=10.1111/j.1365-2958.2007.05740.x | volume=64 | issue=5 | title=Class I and class II lysyl-tRNA synthetase mutants and the genetic encoding of pyrrolysine in Methanosarcina spp |date=June 2007 | journal=Molecular Microbiology| pages=1306–18 | last1=Mahapatra | first1=A | last2=Srinivasan | first2=G | last3=Richter | first3=K. B. | last4=Meyer | first4=A | last5=Lienard | first5=T | last6=Zhang | first6=J. K. | last7=Zhao | first7=G | last8=Kang | first8=P. T. | last9=Chan | first9=M | last10=Gottschalk | first10=G | last11=Metcalf | first11=W. W. | last12=Krzycki | first12=J. A. | s2cid=26445329 }}</ref>