have their amino acid sequences written from the n-terminus
N-terminus The N-terminus (also known as the amino-terminus, NH2-terminus, N-terminal end or amine-terminus) is the start of a protein or polypeptide referring to the free amine group (-NH2) located at the end of a polypeptide. Normally the amine group is bonded to another carboxylic group in a protein to make it a chain, but since the end of a protein has only 1 out of 2 areas chained, the free amine group is referred to the N-terminus. By convention, peptide sequences are written N-terminus to C-terminus, left to right in LTR languages.[1] This correlates the translation direction to the text direction (because when a protein is translated from messenger RNA, it is created from N-terminus to C-terminus - amino acids are added to the carbonyl end).