7
A. ATTENUATION MECI1ANISM
B. TRANSI ATIONAI. INHIBITION
Si gnał metabolitc In n <i*
mRNA
Translaiion
proceeds
.Signal mctabolitc binds
Signal
metabolit?
uuuu
Terminator
PREMATure
1KK\1\AII0X
FIGURĘ 11.18 Riboswitch Mechanisms
Riboswitches alternate between two altema»ive stem and loop structures depending on the presence or absence of the signal metabolite. (A) In the atlenoation mechanism, the presence of the signal metabolite results in formałion of tbe terminator structure and transcripłion is aborted (B) In tbe translational inbibition mechanism, tbe presence of tbe metabolite results in sequestration of tbe Shine-Dalgarno sequence, which prevents translation of the mRNA.
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