Page 38 - The Miracle of Protein
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36 THE MIRACLE OF PROTEIN
More detailed studies revealed the important reason why
the amino acids, except a few bacteria, constituting proteins are
all left-handed. Just like their left-handed counterparts, right-
handed amino acids can combine with one another to form
amino acid chains, but they prevent the resulting protein from
assuming a three-dimensional shape. Yet—as you will see in
due course—in order for a protein to discharge its functions in
living things, it absolutely must assume the correct three-di-
mensional form. It was realized that this being so, all amino
acids had to be among left-handed ones in order for a useful
protein to emerge. The inclusion of even one right-handed
amino acid often prevents the formation of a functional protein.
There are both right-handed and left-handed amino acids in nature.
But only left-handed amino acids are used in protein construction.
Left-handed amino acids Right-handed amino acids
