Subunit complex III-IV as the nucleotide binding site of Qβ replicase

Substrate, metal and template effects on inhibition of bacteriophage-qβ ribonucleic acid polymerase by ortho- and pyro-phosphate

“…As with template, the possibility exists that the effect of GTP on inhibition is related to the existence of two binding sites on phage-Qfl RNA polymerase. Hori (1974) found, on the basis of inhibition by a thiol-blocking reagent, that this enzyme contains both a unique GTP-binding site and a second GTP-binding site shared by the other nucleoside triphosphates. Fedoroff & Zinder (1972) concluded, on the basis of the second-order dependence of reaction rate on GTP concentration, that the related phage-f2 replicase has two substrate-binding sites.…”

“…The study of RNA synthesis in vitro is made complex by the numerous components of polymerase reactions, including four substrates, a template and/or primer nucleic acid, a bivalent-metal cofactor, and additional regulatory proteins (Mueller, 1971 ; Franze de Fernandez et al, 1972;Stevens, 1972;Hoffman & Niyogi, 1973). Further, RNA polymerases, either DNAor RNA-dependent, are multi-subunit structures (Burgess, 1969;Kamen, 1970;Landers et al, 1974) that may contain more than one substratebinding site (Wu & Goldthwait, 1969; Hori, 1974). The functions of these components in normal RNA synthesis have not been fully delineated.…”

“…Similar kinetics were seen for the poly(C)-dependent reaction of bacteriophage-f2 replicase (Fedoroff & Zinder, 1972). Mitsunari & Hori (1973) did not report a non-linear plot for phage-Q15 poly(C)-dependent RNA polymerase, but Hori (1974) has shown that there are two GTP-binding sites on this enzyme.…”

Inhibition of bacteriophage-Q β ribonucleic acid polymerase by guanosine triphosphate analogues

“…Thus GTP is the only ribonucleotide with which normal RNA synthesis is initiated (Hori et al, 1967;Spiegelman et al, 1968;Banerjee et al, 1969). Hori (1974) found that there are two binding sites for GTP on bacteriophage-QI? replicase: one site is shared with the other three nucleoside triphosphates and the other is a unique GTP-binding site where binding is inhibited by the thiol-blocking reagent, p-chloromercuribenzoate.…”