“The dark proteome could be an evolutionary playground for trying out new folds
Ultimately one would expect particularly useful variations to get fixed at the genetic level. But it needn’t be where that variation begins. What’s more, organisms needn’t be quite so dependent for their molecular repertoire on their evolutionary heritage. O’Donoghue thinks that all organisms probably have a significant fraction of proteins unique just to them.
‘The fact that the dark matter of the proteome has less evolutionary constraint than the other bits of proteome may suggest that it’s under less selection,’ says Gerstein. ‘This is perhaps because it’s more flexible structurally, but also in a sense more flexible in terms of accommodating various amino-acid changes compared to the structurally inflexible and fixed parts of the crystallised proteome.’ This adds momentum to the picture of genomics as a rather more fluid affair than is suggested by the old picture of identical proteins being
mass-produced from a fixed genetic template.
Gerstein feels that studying the dark proteome opens up a host of interesting questions. For example, although known bacteria have a smaller dark proteome than eukaryotes, there’s a huge ‘dark
microbiome’ of unculturable bacteria. Might that be more full of dark proteins – perhaps useful ones?
And what about us? ‘How does the human dark proteome compare to that of eukaryotes as a whole?’ Gerstein wonders. How well, really, do we know ourselves?”
Shedding light on the dark proteome
BY PHILIP BALL13 FEBRUARY 2017