Biology Reference
In-Depth Information
Fig. 12.35 The major
components of the
signal
transduction pathways
in the
living cell.
Red ¼
extracellular space;
Green ¼
cell membrane;
Purple
1.
Primary Messenger
2.
Receptor
¼
intracellular space.
Blue
¼
nucleus. The receptor
in this figure can be either
membrane embedded or
located in the cytosol
3.
Secondary Messenger
4.
Signal Transducing Proteins
5.
DNA-Binding Proterins
6.
Target Genes
7.
Target Gene Products
8.
Functions
Components 4, 5, 6, and 7 in Fig.
12.35
cooperate inside the cell to produce
intracellular dissipative structures
(IDSs or
dissipatons
) that are thought to deter-
mine (or are identical with) cell functions. The principle of their operation can be
described in two complementary ways, based on either (1) the
energetic/structural
perspective
or (2) the
semiotic/linguistic perspective
. The energetic/structural prin-
ciple underlying the workings of Components 4-7 is generally known as
“protein-protein interactions” where
structural complementarity
and
free energy
of binding
play fundamental roles. In contrast, the semiotic/linguistic principles
underlying the operation of Components 4-7 are rarely discussed in the current
literature on signal transduction, one exception being the cell language theory (Ji
1997a, b). According to the cell language theory (Sect.
6.1.2
), the linear sequence
of Components 4-7 in Fig.
12.34
can be viewed as
molecular sentences
and hence
the principles of (1) double (or triple) articulations and (2) syntagmatic and
paradigmatic relations should apply to them.