A recombinantly expressed nucleotide triphosphate transporter efficiently imports the triphosphates of unnatural nucleotides into cells, and the endogenous cellular machinery incorporates those nucleotides into cellular nucleic acids. UBPs can therefore form within the cell's nucleic acids. Moreover, neither the presence of the unnatural triphosphates nor the replication of the UBP represents a significant growth burden. The UBP is not efficiently excised by nucleic acid repair pathways, and therefore can be retained as long as the unnatural triphosphates are available in the growth medium. Thus, the resulting cell is the first organism to stably propagate an expanded genetic alphabet.
重组表达的核苷酸
三磷酸转运体能有效地将非天然核苷酸的
三磷酸酯导入细胞,而内源性细胞机制则会将这些核苷酸整合到细胞核酸中。因此,细胞核酸中会形成 UBPs。此外,非天然
三磷酸酯的存在和 UBP 的复制都不会对生长造成重大负担。核酸修复途径不能有效地清除 UBP,因此只要生长
培养基中存在非天然
三磷酸盐,UBP 就能保留下来。因此,由此产生的细胞是第一个稳定繁殖扩增遗传字母的
生物体。