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at in-frame UAGs in some methyltransferases of methanogenicArchaea. Rather, these codons serve as sense codons and, as determined by crystal structure analysis, UAG encodes pyrrolysine, that is, lysine with the epsilon nitrogen in amide linkage to (4R, 5R)-4-substituted-pyrroline-5-carboxylate, the 22nd amino acid found to be genetically encoded in nature. A key question is whether the UAG-translating tRNAcua is first charged with lysine and then modified to pyrrolysine for incorporation into the growing polypeptide or whether pyrrolysine is attached as the fully synthesized amino acid to tRNAcua. Here we show that the latter possibility is feasible by demonstrating the direct pyrrolysylation of tRNAcua in vitro. This is the first example found in nature of specific aminoacylation of tRNA with a non-canonical amino acid. The results reported show further that the expression of only two genes, pylT and pylS, which encode tRNAcua and pyrrolysyl-tRNAsynthetase, can expand the genetic code of E. coli to include pyrrolysine. This procedure could potentially be used to immediately expand the genetic code of any species that can incorporate exogenously added pyrrolysine.

Conclusion:

The current data indicate that pyrrolysine is encoded in DNA using the general mechanism employed for the common set of 20 amino acids. Direct charging of pyrrolysine onto tRNAconstrasts with selenocysteine, a genetically encoded non-canonical amino acid synthesized only on tRNA. Several systems have been recently developed to expand and manipulate the genetic code to generate recombinant proteins containing unnatural amino acids. By adding pylS and pylT genes, it should now be possible to generate proteins with the 22nd amino acid incorporated at UAG targeted sites in any species that can incorporate added pyrrolysine, thereby adding a unique natural amino acid with electrophilic properties. We are now focusing on the pyrrolysine biosynthetic pathway, which offers the possibility of also adding genes that will generate pyrrolysine internally in recombinant organisms.

8. From Aviya Kushner, “McCulture” in The Wilson Quarterly (2009).

Introduction:

As a child, I lived in a house where we spoke only Hebrew. I remember relatives from the American side of the family complaining about my parents’ language policy when they visited our house in New York. “She’ll suffer if she doesn’t speak English at home,” one worried. “She won’t be able to write well enough to get into college.” But something unexpected happened as my Israeli mother sang the Psalms to my siblings and me while we bathed: empires fell. The Berlin Wall literally came down. Droves of immigrants and refugees—huddled masses who had long yearned to be free— changed London, Berlin, Tel Aviv, and New York. India rose, China skyrocketed, and four young Israelis invented instant messaging. Bilingual kids like me, toting odd foods at lunch and speaking with their mothers in something unintelligible, were suddenly not the problem, but the glittering future.

Conclusion:

This is not to discount the value of bilingual writers. There are bilingual writers who feel a special freedom in English: a rebirth, they say, without the weight of culture or history, the taste of prayer or the memory of genocide. Olga Grushin, at the end of our conversation, quoted Charlemagne, who said that to have a second language is to possess a second soul.

I was moved by the idea of another soul. But then I thought it over, as reader instead of writer. As praise is heaped on people who have mastered English, we are rewarding writers for selling their first soul. A culture with a healthier translation climate would create a space between languages, a space between souls. As readers, we’d win. We’d be able to hear the sound of all sorts of souls on the page—whether a first soul or, as Charlemagne claimed, a second soul, trying to speak, or perhaps, with luck, sing.

GUIDELINES FOR WRITING INTRODUCTIONS AND CONCLUSIONS

Introductions

1. The introduction seeks to raise the issue, not settle it.