Page 136 - The Miracle of Protein

134 THE MIRACLE OF PROTEIN

sisting of substances like carbon, oxygen, and nitrogen manage
to do this regularly, without making a single error?
Tubulin molecules select other molecules of their own
kind from among all the millions of molecules around them,
move alongside them and immediately assume their places.
Tubulins can easily contact with microtubules, but micro-
tubules need the help of other proteins to combine with one an-

other. The nine rods that make up the microhair must combine
together, but need other proteins to do so, and for a very good
reason: microtubules are proteins with very different functions
within the body. In order to be able to carry out their duties,
they need to be separate and independent to function. For that
reason, they rove independently until binding to another pro-
tein. But in order for tubulins to form, these helper proteins
come and select free and independently traveling microtubules
and bind them to one another. This process requires a con-

scious and purposeful organization. Certain proteins determine
that the cell's minute hairs should be constructed, know what is
needed for their formation of these, and gather up and combine
these materials.
Electron microscope photographs of these tiny hairs show
that different kinds of connectors bind the microtubules to one
another. There exist one protein at two centers in the middle of

the microtubules that binds them together in the form of a
bridge. There is also an extension from the microtubules to the
center of the tiny hairs. A protein known as nexin binds each
microtubule to the one beside it, ensuring that they do not
break away and disperse. There are also two different protru-
sions on every microtubule, known as the inner arm and the
outer arm. Biochemical analyses have revealed that each con-
tains a protein called dynein. Among the functions of dynein,