Nature emulating humans

Most of the early manmade polymers consisted of a repeating monomers. In proteins - the biological polymers - this is rare. You could have up to different 20 amino acids in a protein. So when you find a  single monomer based protein, you will sit up and take note. Proteins having long stretches of amino acids like lycine and glutamate are well documented. But when a protein of more than 300 amino acids has only the amino acid called serine - well, it becomes serious.

Serine sequences are coded with a lot of degeneracy: there are six different three letter codes for serine So minor changes in the DNA code at single nucleotide level does not make much difference to the ultimate serine sequence. So it is highly conserved.

And usually, if a protein is highly conserved, it must have some major function. The paper which reports this in a recent issue of the journal Heredity does not explore the functions of the protein. But knowing the central role of the amino acid serine play in the synthesis of nucleotides and also as a precursor to some amino acids, we should expect that a protein made of serine too has very important functions in the cell.

The homopolymer of serine was discovered in a soil amoeba called Dyctyostelium. Dyctyostelium goes through a life cycle consisting of unicellular and multi-cellular  forms and has been used as a model for understanding social organisation. So we should expect that such sequences exist in many other organisms soon.

 Heredity 112, 215-218 (February 2014) | doi:10.1038/hdy.2013.96