Proteins are a hotly researched area of drug design, but proteins can be degraded by the human body. Protein rings, however, are super-stable, giving them greater potential as drugs.
The main way to make protein rings is by chemical synthesis, but this is costly, inefficient and uses toxic chemicals. However, we have worked out how sunflowers turn a protein string into a super-stable protein ring in their seeds.
The enzyme that performs this ring-forming reaction is one that usually cuts proteins, but instead of using water to finish the job it uses the head of a protein chain to form a new bond instead of breaking one. The ability to develop water-based reactions will eliminate the need for expensive and harmful chemical synthesis of drugs that are stable protein rings.
The work on this unusual ring-forming reaction began with a small protein found in the seeds of sunflowers called SunFlower Trypsin Inhibitor 1. SFTI-1 is a ring of 14 amino acids that has no head or tail.
SFTI-1 was discovered in the late 1990s and became popular with synthetic protein drug designers, but only in 2011 did the gene that encodes SFTI-1 become known. The sequence for SFTI-1 is buried inside a gene that also makes seed storage albumin, a protein that accumulates to very high levels in seeds before degrading during germination to provide nutrients for the growing...
