Page 38 - The Miracle of Protein
P. 38

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
   33   34   35   36   37   38   39   40   41   42   43