MODIFIED NUCLEOSIDE 5'-TRIPHOSPHATES CONTAINING ADDITIONAL 2',3'-FUSED CYCLE AS SUBSTRATES FOR DNA-POLYMERASES

It was shown that 5'-triphosphates of 1-(2',3'-epithio-2',3'-dideoxy-beta-D-lyxofuranosyl)thymine (ItTTP), 1-(2',3'-epithio-2',3'-dideoxy-beta-D-ribofuranosyl)thymine (rtTTP), and 2',3'-lyxoanhydrothymidine (laTTP) are terminating substrates for HIV and AMV reverse transcriptases and E. coli DNA polymerase I, but do not terminate DNA synthesis catalyzed by DNA polymerase E from human placenta. The Michaelis constant for incorporation of ltTTP, rtTTP, and laTTP into the growing DNA chain are close to each other and 1.5-2.5-fold higher than that for dTTP. Their V-max values are only two-threefold lower than that for dTTP. The data obtained support the hypothesis that modified substrates with a flattened glycon have high affinity to the active centers of DNA polymerases.