Transfer RNA and the Control of the Histidine Operon

Using Studies on Tryptophan Metabolism to Answer Basic Biological Questions

“…The experimental results of Bruce Ames and his co-workers at the University of California, Berkeley, were of particular interest to us because the his operon of Salmonella they were studying and our trp operon had many similarities. Ames showed that transcription of the his operon was not regulated by a histidine-responsive his repressor; rather, histidinyl-tRNA was implicated as the molecule that was sensed in the regulatory decision (58). Furthermore, the leader region of the his operon, not its promoter, appeared to be the site of regulation.…”

Regulation of Amino Acid Metabolism

“…From tlaese studies it is clear that histidyl tRNA is also involved in repression of the histidine operon. While such an observation does not eliminate an operator-repressor model in which it is the histidyl tRiVA ra!.her than free hlstidine which activates the repressor, it does invite speculation that repression is coupled directly to translation rather than to transcription, such as the mechanism suggested by Roth et al (110) or by the Vogel (185).…”

“…Similarly, evidence for an aporepressor for the leucine pathway is also lacking. On the other hand, a purely translational model involving active participation of the branched-chain amino acyl tRNA's could be postulated based upon that proposed several years ago by Roth et al (110). However, at least until some of the existing mutants have been examined more thoroughly, such speculation is quite premature.…”

Mirroring, Symbolism and Need: A Two-Timing Nature or a Whole Concept

“…al. , 2003, Roth et. al., 1966, in higher organisms the Hox genes are all clustered together, regulated and arranged in a a non-random sequence that matches the order of events during overall physical development and are linearly arranged in the DNA in the same order as the development of components of structures such as limbs, body and head (Myer, 2008), and in bacteria the rigid structure of the cell wall attributed to the temporal order of assembly and arrangement of components is reported to find explanation within the physical arrangement and structure of the region of DNA containing the genes that code for it (Danchin et.…”