IUB/IUPAC set a format where the letters A-Z are used to represent a chain of amino acids, instead of spelling out ACGT/U of DNA and RNA. Many lines of the file are accessions of Major prion protein from humans and other mammals. This protein is believed to normally serve a complex role in the brain and nervous… See the full description on the dataset page: https://huggingface.co/datasets/scarysnake/prion-fasta.