Page 134 - The Miracle of Protein

132 THE MIRACLE OF PROTEIN

mands them to join together with other tubulin molecules and

then set themselves out in cylindrical form? How can they take
this order, understand and implement it? In addition, the tubu-
lin molecules are laid out, not in a random sequence, but in an
order compatible with their pattern and purpose.
Under normal conditions (that is, normal calcium levels
and specific temperature have been established within the cell),
the tubulin proteins that serve as bricks come together auto-
matically to form microtubules. The surfaces of tubulin mole-
cules are such that one side fits the back of a second tubulin

molecule. A third tubulin molecule attaches itself to the back of
the second, a fourth molecule then attaches to the back of the
third, and so forth. To make a comparison, this system resem-
bles a stack of tin cans of the same brand, one on top of the oth-
er, each one arranged to fit perfectly into the top of the can be-
low it. In this order of alignment, where the top of the second

can fit properly to the bottom of the third, there is no risk of
toppling. However, since the tops and bottoms of cans of differ-
ent brands will not fit perfectly together, if piled atop one an-
other, they will collapse at the slightest movement. And cans of
the same brand will still topple over if you do not properly align
them. The top of the first can will not fit the top of the next one,
and so they will topple over. The order within the assembly of
the tubulin proteins is much more exact, in that the front of one
fits exactly into the other one’s back. 58

So, who created this arrangement? Could the cells that
produce the tubulin proteins have determined how to assemble
them in the most efficient manner? Assuming that the proteins
were produced with these features in some way, who told them
to arrange themselves back to front, and not back to back?
Moreover, how did the proteins understand this command and