Edit: A true expert would never define a problem in such a sloppy way:
"Specifically, the protein must convert N₂ to ammonia at rates that are at least of a similar order of magnitude to the rates of naturally occurring proteins, and must fall well below the sequence- and structure-similarity thresholds relative to all known nitrogenase and nitrogenase-like proteins. The protein may be designed de novo, discovered in nature, or engineered or evolved from naturally occurring starting points."
Edit: A true expert would never define a problem in such a sloppy way: "Specifically, the protein must convert N₂ to ammonia at rates that are at least of a similar order of magnitude to the rates of naturally occurring proteins, and must fall well below the sequence- and structure-similarity thresholds relative to all known nitrogenase and nitrogenase-like proteins. The protein may be designed de novo, discovered in nature, or engineered or evolved from naturally occurring starting points."