Page 154 - The Miracle of Hormones

THE MIRACLE OF HORMONES

the transfer of information among cells.
The nerve cells in the brain cells (neurons) or eye cells actually have
the fastest known capacity for the transfer of information.
In these cells are systems functioning at every moment to make the
transfer of information fast and without error. The latest research on the
communication web of nerve cells has shown that some proteins in neu-
ronal pathways have an "incredibly large number of linker domains." 47
Therefore, these proteins are able to hold groups of messenger proteins
together permanently. The very rapid communication in nerve cells is
the result of this special design.
As an example of the special proteins that have a role in the commu-
nications mechanism in the world of cells, we will consider PSD-95. This
messenger protein is thought to be an agent in the neurons related to
learning.
In the linker modules of the PSD-95 protein are three PDZ domains.
The first of these attaches to the tail of the receptor in the cytoplasm; the
second controls the ion channel in the membrane of the cell; the third
grasps the messenger proteins in the cytoplasm. In other words, the
linker modules in the structure of PSD-95 makes it possible for it to coor-
dinate several elements of communication at the same time.

PDZ is one of the various linker modules of the PSD-95 protein. In the
first picture, you can see the structure of the PDZ module. In the picture
on the right, the red areas are the PSD-95 protein.

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