Multisite Phosphorylation Provides an Effective and Flexible Mechanism for Switch-Like Protein Degradation
Figure 1
Phosphorylation-triggered degradation of a multisite protein.
(A) A single kinase and a single phosphatase act on an -site protein in a random order. Each oval represents a distinctly phosphorylated state of the substrate protein S and the subscript indicates whether or not each site is phosphorylated (e.g. 10100 means that the 1st and 3rd sites out of fives sites are phosphorylated). The protein becomes degradable (highlighted in red) if
or more sites are phosphorylated. (B) The special case of a fully sequential system. The superscript of S indicates how many sites are phosphorylated. (C) Kinetic parameters for sequential phosphorylation and dephosphorylation:
,
and
stand for kinetic rate constants of phosphorylation, dephosphorylation and degradation, respectively.
for
and
for
. (D) The output of the model is shown for a random system with the following parameters:
,
,
,
,
for
and
for
,
,
.