Adaptive protein coevolution preserves telomere integrity.

Many essential conserved functions depend, paradoxically, on proteins that evolve rapidly under positive selection. How such adaptively evolving proteins promote biological innovation while preserving conserved, essential functions remains unclear. Here, we experimentally test the hypothesis that adaptive protein-protein coevolution within an essential multi-protein complex mitigates the deleterious incidental byproducts of innovation under pressure from selfish genetic elements.