Protein Structure to Function
Country: United States
Date: January 2009
What is it about proteins that allow for some many
potential functions? Twenty amino acids and seemingly unlimited
If the average protein is around 150 amino acids long and there is no
restriction on amino acid sequence, the number of different proteins
possible would be larger than the estimated number of atoms in the universe.
Ron Baker, Ph.D.
Think of amino acids as a 20 letter alphabet. Each protein is a textbook.
There are some grammar rules about how to construct "words", "phrases", "sentences",
"paragraphs", "pages", and "chapters" of a "textbook". Change any one of the above
results in a different "textbook" even after the grammar rules have to be obeyed.
Some "textbooks" can be longer or shorter, and even some of its components can be
different. Without doing a calculation it is clear that there are an enormous
number of combinations of this 20 letter alphabet, even if there are a large number
of possible "textbooks" possible, that do not "survive". Those combinations that
don't replicate, or those that don't survive their environment, fail. Even so the
number of possibilities are a very large number. That is how "evolution" selects
combinations that survive, or adapt to different parts of the "textbook".
If you think about the amino acids being like letters in the alphabet, there are many
many words that can be created with just 26 letters, depending on how they are arranged.
The slightly different chemical characteristics of the various amino acids are what
determine the chemical behavior and functions of the proteins created from them when
arranged in different sequences.
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Update: June 2012