Tropomyosin Isoforms and Evolution
In direct contrast of the ‘one gene, one polypeptide’ rule, we now know from a combination of genomic sequencing, such as the Human Genome Project and EST data of expressed proteins that many eukaryotes produce a range of proteins from a single gene. This plays a crucial role in the functionality of higher eukaryotes, with humans expressing more than 5 times as many different proteins (isoforms) through alternative splicing than they have genes. From a mechanistic point of view it is much easier for an organism to expand on a current gene/protein family (creating protein isoforms) than it is to create an entirely new gene. From an evolutionary point of view, tropomyosins in higher eukaryotes are notable in retaining all 4 of the potential genes produced by the dual genomic duplication event that took place in early eukaryotic evolution.
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