The test is a colorimetric assay which measures the expression of genes induced by genotoxic agents in " Escherichia coli ", by means of a fusion with the structural gene for ?-galactosidase.
32.
The E . coli rrn operons are regulated by an antitermination mechanism that is dependent on sites that are closely related to lambda " boxA " and located promoter proximal to the 16S and 23S structural genes in each operon.
33.
The structural gene sequence of HPIVs is as follows : "'32-NP-P-M-F-HN-L-52 "'( the protein prefixes and further details are outlined in the table below ).
34.
"' nifHDK operon "': comprises three structural genes : nifK nifD and nifH . nifK encodes for B-subunit of Component 1 of nitrogenase . nifD encodes for alpha subunit of component 1 of nitrogenase . nifH encodes for component 2 of nitrogenase.
35.
The phenotype of a cell carrying one mutant and one wild type operator site is that LacZ and LacY are produced even in the absence of the inducer IPTG; because the damaged operator site, does not permit binding of the repressor to inhibit transcription of the structural genes.
36.
These two synthetases, which are both referred to as the AsnC protein, are coded for by two genes : AsnA and AsnB . AsnC is autogenously regulated, which is where the product of a structural gene regulates the expression of the operon in which the genes reside.
37.
Thus, three distinct secondary structures ( transcription termination sequence ( abundant in G / C and immediately followed by several uracil residues ), once it forms RNA polymerase will disassociate from the DNA and transcription of the structural genes of the operon can not occur ( see below for a more detailed explanation ).
38.
A more sophisticated version of this experiment uses " marked " operons to distinguish between the two copies of the " lac " genes and show that the unregulated structural gene ( s ) is ( are ) the one ( s ) next to the mutant operator ( panel ( g ).
39.
"' HutP "'( "'Histidine utilizing Protein "') is one of the anti-terminator proteins of " Bacillus subtilis ", which is responsible for regulating the expression of the hut structural genes of this organism in response to changes in the intracellular levels of L-histidine and divalent metal ions.
40.
For example, the following names are used for members of this group, but also for unrelated proteins : HupD is used in " Azotobacter chroococcum " and " Anabaena " species to designate an unrelated hydrogenase maturation factor; HydD is used to designate hydrogenase structural genes in " Thermococcus litoralis ", " Pyrococcus abyssi ", and other species.
