Past exam of the biochemistry course of the University of Cambridge / 2025 / Paper 5 / Section 2 / 2 / g / Solution 2026-10-20
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Reusable protein domains make evolution combinatorial: a new domain combination can join an existing catalytic activity to a binding, localization or regulatory module without inventing every component anew. Gene duplication allows one copy to retain an established role while another diverges; domain shuffling and fusion can create new combinations. Connecting domains can also increase effective local concentration of interacting sites or enable allostery.
These are potential advantages, not guarantees that every fusion is beneficial: domains must still fold and work together. The domain-level analysis behind this example found extensive reuse and new combinations of recognized structural units.[ref]
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