For decades, scientists have known that the sequence of amino acids that make up a protein determines the protein's structure and its function. What has not been known is what information contained within that sequence produces the proper structure.
All proteins are made up of 20 specific amino acids. Even for a small protein made up of 100 amino acids, the number of possible combinations of amino acids is staggering, many times more than the number of atoms in the known universe.
"How did nature devise the right sequences that resulted in functioning proteins? Somehow, it found a way," Dr. Ranganathan said. "One implication of our work is that the evolutionary protein-design process may not be as complex as was previously thought."
Earlier research has shown that for a given group of related proteins, or protein family, all family members share common structures and functions. By examining more than 100 members of one protein family, the UT Southwestern group found that the proteins share a specific pattern of amino acid selection rules that are unique to that family.
"What we have found is the body of information that is fundamentally ancient within each protein family, and that information is enough to specify the structure of modern-day proteins," Dr. Ranganathan said.
He and his team tested their newly discovered "rules" gleaned from the evolutionary record by feeding them into a computer program they developed. The program generated sequences of amino acids, which the researchers then "back-translated" to create artificial genes. Once inserted into laboratory bacteria, the genes produced artificial proteins as predicted.
"We found that when isolated, our artificial proteins exhibit the same range
Source:UT Southwestern Medical Center