Absolute configuration of the diastereomers of adenosine 5'-O-(1-thiotriphosphate): consequences for the stereochemistry of polymerization by DNA-dependent RNA polymerase from Escherichia coli.

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Abstract
The diastereomers of uridyl-(3''-5'')adenyl-O,O-phosphorothioate [Up(S)A] were separated by high-performance liquid chromatography. Their identification as Rp and Sp follows from the RNase A digestion of these products. It was then shown, by the same method, that the R isomer is hydrolyzed by snake venom phosphodiesterase (PDEase) approximately 500 times faster than the S isomer. Similarly, the stereoisomer of adenosine 5''-O-(1-thiotriphosphate) (ATP.alpha.S), until now arbitrarily designated as isomer B, is hydrolyzed approximately 400 times faster by PDEase than is isomer A. Apparently, the R isomers of Up(S)A and ATP.alpha.S, isomers B, have the same absolute configuration. It then follows that isomer A of ATP.alpha.S, the preferred of the 2 isomers as substrate for DNA-dependent RNA polymerase, has the S configuration. The implications for the stereochemistry of action of the latter enzyme are discussed.