How are modified amino acids represented in sequence listings?

This page is an FAQ based on guidance from the Manual of Patent Examining Procedure. It is provided as guidance, with links to the ground truth sources. This is information only: it is not legal advice.

Modified amino acids in sequence listings are represented according to specific guidelines outlined in MPEP 2412.05(d):

• Modified amino acids should be represented as the corresponding unmodified amino acid in the sequence itself whenever possible.
• The modified amino acid must be further described in the Feature section of the sequence listing.
• As stated in the MPEP, “The feature key “MOD_RES” should be used, along with the abbreviation for the modified amino acid as the qualifier value.“

This approach ensures that the sequence can be properly interpreted while still providing information about modifications.