INTERACTIONS OF 2'-MODIFIED AZIDOANALOGS AND HALOANALOGS OF DEOXYCYTIDINE 5'-TRIPHOSPHATE WITH THE ANAEROBIC RIBONUCLEOTIDE REDUCTASE OF ESCHERICHIA-COLI
R. Eliasson et al., INTERACTIONS OF 2'-MODIFIED AZIDOANALOGS AND HALOANALOGS OF DEOXYCYTIDINE 5'-TRIPHOSPHATE WITH THE ANAEROBIC RIBONUCLEOTIDE REDUCTASE OF ESCHERICHIA-COLI, The Journal of biological chemistry, 269(42), 1994, pp. 26116-26120
The anaerobic Escherichia coli ribonucleotide reductase (class III red
uctase) responsible for the synthesis of the deoxyribonucleotides requ
ired for anaerobic DNA replication contains an oxygen-sensitive glycyl
radical (Gly-681) suggesting involvement of radical chemistry in cata
lysis. The amino acid sequence of this enzyme completely differs from
that of earlier described aerobic class I (prototype, aerobic E. coli)
and class II (proto type, Lactobacillus leichmanii) reductases that u
se radical chemistry but employ other means for radical generation. He
re, we study the interaction between the anaerobic E. coli reductase w
ith the 5'-triphosphates of 2'-chloro-2'-deoxycytidine, 2'-fluoro-2'-d
eoxycytidine, and 2'-azido-2' deoxycytidine (N3CTP), which are mechani
sm-based inhibitors of class I and II reductases and, on interaction w
ith these enzymes, decompose to base, inorganic di(tri)phosphate and 2
'-methylene-3(2H)-furanone. Also, with the anaerobic E. coli reductase
, the 2'-substituted nucleotides act as mechanism-based inhibitors and
decompose. N3CTP scavenges the glycyl radical of the enzyme similar t
o the interaction of N3CDP with the tyrosyl radical of class I enzymes
. However we found no evidence for a new transient radical species as
is the case with class I enzymes. Our results suggest that the chemist
ry at the nucleotide level for the reduction of ribose by class III en
zymes is similar to the chemistry employed by class I and II enzymes.