Reversibility of the Pyrophosphoryl Transfer from ATP to GTP by Escherichia coli Stringent Factor

AUTOR(ES)

Sy, Jose

RESUMO

The stringent factor-catalyzed, ribosome-dependent synthesis of guanosine polyphosphates is found to be reversible. The reverse reaction specifically requires 5′-AMP as the pyrophosphoryl acceptor, and guanosine 5′-triphosphate-3′-diphosphate is preferentially utilized as the pyrophosphoryl donor. The primary products of the reaction are GTP and ATP. The reverse reaction is strongly inhibited by the antibiotics thiostrepton and tetracycline, and by ATP and β-γ-methylene-adenosine-triphosphate, but not by ADP, GTP, and GDP. The reverse reaction occurs under conditions for nonribosomal synthesis. The overall reaction for stringent factor-catalyzed guanosine polyphosphate formation may thus be formulated: (p)pp5′G + ppp5′A ⇌ (p)pp5′G3′pp + p5′A.

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