Biology Reference
In-Depth Information
Fig. 11. Simulation results of the lac repressor mutant. Concentrations of proteins LacZ and LacY keep growing, since the
mutants
lacI
−
and
lacI
−d
lose the ability to bind at the operator site. In the mutant
lacI
s
, the transcription of the lac operon
does not begin, since the repressor can not be removed from the operator site.
protein begins to be produced. By comparing the concentration behavior of lactose and lactose (outside
of a cell), we can know that the LacY protein works well. At time point 65 the concentration of
LacZ exceeds 10, decomposition of lactose to glucose and galactose starts, increasing the concentration
of glucose again. Just after the glucose is once again completely consumed, the transcription of the
lac operon is stopped, keeping the concentration of LacZ and LacY proteins at some levels (from the
assumption that the degradation speed of these proteins is very slow) [Alberts
et al.,
1994; Lewin, 1997].
Behavior of the lac repressor mutant
Figure 11 shows the simulation results of the mutants
lacI
−
,
lacI
s
, and
lacI
−d
obtained from GON.
In the
lacI
−
and
lacI
−d
mutants, LacZ protein and LacY protein are produced, while these proteins are
not produced in the
lacI
s
mutant. Furthermore, in the
lacI
−
and
lacI
−d
mutants, the concentrations
of LacZ and LacY proteins keep growing (except during the period of glucose re-production), even
after the decomposition of lactose has ended. Note that these simulation results support the biological
experimental results [Alberts
et al.,
1994; Lewin, 1997].
