I'd like to add a short peptide to the C terminus of each protein (around 1000 in total) in the fasta file from Uniprot database. Could you give me some clues how to do that? Thank you so much!
Try seqkit mutate.
$ echo -ne ">a\nATCG\n>b\ngcat\n"
$ echo -ne ">a\nATCG\n>b\ngcat\n" | seqkit mutate -i -1:NNNN
[INFO] edit seq: a
[INFO] edit seq: b
linearize the fasta and add the suffix with sed 's/$/blablabal/'