Expression of the glycolytic gapA operon in XXXX : differential syntheses of proteins encoded by the operon.

@entity1522 @entity505 @entity3881 @entity3363 @entity16335
Glycolysis is one of the central routes of @entity505 catabolism in @entity3881 . Several glycolytic enzymes, including the key enzyme @entity16335 dehydrogenase, are encoded in the hexacistronic gapA operon. Expression of this operon is induced by a variety of @entity3363 and @entity1522 . Under non-inducing conditions, expression is repressed by the CggR repressor protein, the product of the promoter-proximal gene of the operon. Here, it is shown that the amount of @entity16335 dehydrogenase encoded by the second gene of the operon exceeds that of the CggR repressor by about 100-fold. This differential synthesis was attributed to an mRNA processing event that takes place at the 3' end of the cggR open reading frame and to differential segmental stabilities of the resulting cleavage products. The mRNA specifying the truncated cggR gene is quickly degraded, whereas the downstream processing products encompassing gapA are quite stable. This increased stability is conferred by the presence of a stem-loop structure at the 5' end of the processed mRNAs. Mutations were introduced in the region of the cleavage site. A mutation affecting the stability of the stem-loop structure immediately downstream of the processing site had two effects. First, the steady-state transcript pattern was drastically shifted towards the primary transcripts; second, the stability of the processed mRNA containing the destabilized stem-loop structure was strongly decreased. This results in a reduction of the amount of @entity16335 dehydrogenase in the cell. It is concluded that mRNA processing is involved in differential syntheses of the proteins encoded by the gapA operon.
