<Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (January 2017) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (January 2017) (Learn how and when to remove this template message) </Td> </Tr> <P> The N - terminus (also known as the amino - terminus, NH - terminus, N - terminal end or amine - terminus) is the start of a protein or polypeptide referring to the free amine group (- NH) 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 . 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). </P> <P> Each amino acid has an amine group and a carboxylic group . Amino acids link to one another by peptide bonds which form through a dehydration reaction that joins the carboxyl group of one amino acid to the amine group of the next in a head - to - tail manner to form a polypeptide chain . The chain has two ends--an amine group, the N - terminus, and an unbound carboxyl group, the C - terminus . </P>

Have their amino acid sequences written from the n-terminus
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