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Cyclic phosphates of some antiviral acyclonucleosides: relationship between conformation and substrate-inhibitor properties in some enzyme systems

100%

Ciesla J. M., Stolarski R., Shugar D.

Acta Biochimica Polonica

1993

tom 40

nr 2

Solution conformations, and substrate/inhibitor properties towards several phosphodiesterases and other nucleolytic enzymes, have been investigated for the cyclic phosphates of various acyclonucleosides, some with known antiviral activity, including 9-[(l,3-dihydroxy-2-propoxy)methyl]guanine (DHPG) and its carbocyclic congener, 9-(3,4-dihydroxybutyl)guanine (DHBG), 9-[4-hydroxy-2-(hydroxymethyl)- butyl]-guanine (2HM-HBG), and 9-(2,3-dihydroxypropyl)guanine (HPG). Conformations of the cyclic phosphate rings were derived from analysis of the 1H-1H and 1H-31P vicinal coupling constants in the n.m.r. spectra, subsequently optimalized by minimalization of the internal energy. The resulting structures were examined with respect to their ability to recognize various specific phosphodiesterases and nucleases, and some structural parameters were delineated for acyclonucleotide interactions. Qualitative data are presented for inhibitory properties of the acyclonucleoside cyclic phosphates, and, in those instances where they were substrates, kinetic constants were evaluated. An unusual finding was the apparent ability of nuclease P1 to hydrolyse a five-membered cyclic phosphate ring of an acyclonucleoside.

Cyclases of the 3'-terminal phosphate in RNA: A new family of RNA processing enzymes conserved in Eucarya, Bacteria and Archaea

58%

Filipowicz W., Billy E., Drabikowski K., Genschik P.

Acta Biochimica Polonica

1998

tom 45

nr 4

The 2',3'-cyclic phosphate termini are produced, as either intermediates or final products, during RNA cleavage by many different endoribonucleases. Likewise, ribozymes such as hammerheads, hairpins, or the hepatitis delta ribozyme, generate 2',3'-cyclic phosphate ends. Discovery of the RNA 3'-terminal phosphate cyclase has indicated that cyclic phosphate termini in RNA can also be produced by an entirely different mechanism. The RNA 3'-phosphate cyclase converts the 3'-terminal phosphate in RNA into the 2',3'-cyclic phosphodiester in the ATP-dependent reaction which involves formation of the covalent cyclase-AMP and the RNA-Ni3'pp5'A intermediates. The findings that several eukaryotic and prokaryotic RNA ligases require the 2',3'-cyclic phosphate for the ligation of RNA molecules raised a possibility that the RNA 3'-phosphate cyclase may have an anabolic function in RNA metabolism by generating terminal cyclic groups required for ligation. Recent cloning of a cDNA encoding the human cyclase indicated that genes encoding cyclase-like proteins are conserved among Eucarya, Bacteria, and Archaea. The protein encoded by the Escherichia coli gene was overexpressed and shown to have the RNA 3'-phosphate cyclase activity. This article reviews properties of the human and bacterial cyclases, their mechanism of action and substrate specificity. Possible biological functions of the enzymes are also discussed.

Ograniczanie wyników

2 Acta Biochimica Polonica

1 Billy E.

1 Ciesla J. M.

1 Drabikowski K.

1 Filipowicz W.

1 Genschik P.

1 Shugar D.

1 Stolarski R.

1 1998

1 1993

Wyniki wyszukiwania

Cyclic phosphates of some antiviral acyclonucleosides: relationship between conformation and substrate-inhibitor properties in some enzyme systems

Cyclases of the 3'-terminal phosphate in RNA: A new family of RNA processing enzymes conserved in Eucarya, Bacteria and Archaea