Intrinsically Disordered Proteins overturnes Crick's "Structured Sequence Hypothesis"


The structured sequence hypothesis was first proposed by Francis Crick in 1958. It states that the sequence of bases in the genetic material (DNA or RNA) determines the sequence of amino acids for which that segment of nucleic acid codes, and this amino acid sequence determines the three-dimensional structure into which the protein folds. The three-dimensional structure of a protein is required for a protein to be functional.

This became a key cornerstone of Neo-Darwinism. 


Evolution occurred when a random mutation caused a change in the protein structure. If an improvement occurred natural selection would fix it in place. And so we thought for 50 years.

Recent research on intrinsically disordered proteins (IDPs) and intrinsically disordered regions (IDRs) has shown that this is not the case. IDPs and IDRs are proteins that do not have a well-defined three-dimensional structure, and their function is thought to be mediated by their disordered state.


 This suggests that SSH is not a valid explanation for protein folding and function in at least 51% of proteins. Other research indicates most proteins have some disorder.

In a 2018 paper, researchers from the University of Cambridge and the University of Oxford showed that IDPs and IDRs are more common than previously thought, making up about 40% of all proteins. Researchers at San Diego gave a percentage of 51%. Both showed that IDPs and IDRs are involved in a wide range of cellular functions, including transcription, translation, and signal transduction.

These findings have led some scientists to seriously  question the validity of Cricks SSH and to propose alternative models of protein folding and function. For example, the "random coil hypothesis" states that the three-dimensional structure of a protein is not determined by its amino acid sequence, but rather by the interactions between the amino acids themselves.

The debate over SSH is ongoing, but the discovery of IDPs and IDRs has certainly challenged the traditional neo-Darwinian view of protein folding and function. Our understanding of these processes will likely continue to evolve as we learn more about the role of disordered proteins in biology.


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