Page 42 - The Miracle of Protein

40 THE MIRACLE OF PROTEIN

The Plan in the Amino Acid Sequences
Fulfilling all the conditions described so far is still not suf-

ficient for the formation of proteins. For every protein, a partic-
ular amino acid sequence is required.
Amino acids combine together like the links in a chain. As
soon as the chain is complete, they assume a different shape and
enable the protein to assume a three-dimensional form. As shall
be seen in detail later on, in order for proteins to fulfill their re-

sponsibilities, they must have a three-dimensional structure.
But for this to be so, the amino acid set cannot be deficient in
any way or exchange its place in the sequence with a different
amino acid. The absence or impairment of a single critical com-
ponent will ruin the harmony of the whole and make the pro-

tein's structure inoperable.
This is like changing a single letter in a word, thus chang-
ing its entire meaning or rendering it completely meaningless.
For example, the word "grand" written with a t instead of d will
produce the word "grant," which has a completely different
meaning. If the letter “a” is omitted from "grand," then the
meaningless "grnd" results. The same applies to proteins. A sin-

gle amino acid changing its position will usually impair the pro-
tein’s "meaning" and make it unable to function. In fact, the pro-
tein thus altered will become an entirely different molecule, be-
cause every amino acid endows the protein with a particular
property, just as a change of letter adds a different significance

to a word. With its shape, electrical charge, and manner of en-
tering into chemical reactions, every amino acid resembles a dif-
ferent letter.
Mediterranean anemia, a genetic form of cancer, is an ex-
ample of the kind of damage caused by the faulty or deficient
writing of an amino acid. It is known that erythrocytes in the