Producing proteins costs energy, and producing longer proteins costs more energy than shorter proteins. Producing proteins which have no function, would therefore presumably negatively impact the fitness of a bacteria in culture. So my question is this:

Is there a way of modeling how much a nonfunctional protein would impact fitness relative to the wild-type which doesn't produce this protein? In other words, what is the cost — in terms of fitness — of just producing a protein, if you ignore all the other effects of the protein inside the cell?

How much would the length of the protein effect it? would the impact on fitness vary linearly with the length of the protein?

This would probably depend on many different parameters, I'm just not sure what all of them are and how each of them would factor into the final result. For instance, it would probably depend on the level of expression of the gene (which sigma factor would impact this especially).

I posted a similar question a while ago, but I've reworded it based on feedback from last time. If it helps you to think of a specific organism to answer the question, by all means, do so. Let me know if there is any literature already on a question related to this one!

  • $\begingroup$ I expect any empirical investigation would show there would be more to this than the lost energy spent producing the nonfunctional protein. You could transform a bacterial cell so that it produced this "nonfunctional protein", but it's going to take up space, interact with other macromolecules and cellular components, possibly agglomerate... Cells are crowded. Are you more interested in a theoretical model that ignores these possible effects? $\endgroup$ – De Novo Oct 25 '18 at 4:52
  • $\begingroup$ Yes, my main question was more how one would even begin to create a theoretical model. But the point you raised is a good one. $\endgroup$ – Dylan Slagh Oct 25 '18 at 12:18
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    $\begingroup$ Every transgenic cell we ever made to express some fluorescent protein (FP) is doing this. At least we hope that besides fluorescing, the protein is non-functional (which isn't always the case). It's usually the method of insertion that's more harmful than wasting energy on expressing the protein. Reasoning from the fact that my transgenic fruit flies do horribly compared to wild ones (and it's common knowledge that more insertions = sicker flies), but within one tissue, FP-expressing cells don't get displaced by non-FP-expressing cells of the same type. $\endgroup$ – Armatus Oct 25 '18 at 14:37

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