There are two forms of common polypeptide writing – single letter and three letter form.
Either way. As long as it is the same peptide chain, the polypeptide structure it expresses is the same. The peptide sequences written out are not only understood by ourselves, but also understood by others.
In order to avoid differences in interpretation, the international consensus stipulates that the N-terminal (amino terminal) of the polypeptide is on the left, and the C-terminal (carboxyl terminal) of the polypeptide is on the right.
Single letter writing of polypeptides
As the name suggests, a letter represents an amino acid (easy to record and write). The single letter selection of amino acids is not random. At present, our common one letter rule is mainly 20 kinds of common amino acids, and amino acids are represented by capital letters (L-amino acids).
For example, a stands for alanine, C for cysteine, and G for L-GLYCINE.
If the configuration of an amino acid, such as alanine, is changed, when it is represented by a single letter, we use a lowercase letter. For example, D-alanine is represented by a, isoleucine by I, and methionine by M.
Examples of single letter writing of polypeptide sequence
① The peptide sequence 1: gtflvrcdma contains 10 amino acids, and all the letters are capitalized, indicating that all amino acids are naturally existing L-type amino acids.
Peptide structural formula anto bio mapping
② The peptide sequence 2: gtflvrcdma contains 10 amino acids. Two amino acids in the sequence are lower case, indicating that the corresponding two amino acids are D-type amino acids.
③ Peptide sequence 1: gtflvrcdma can also be written as h-gtflvrcdma-oh. The left h-represents the N-terminal amino group and the right-oh represents the C-terminal carboxyl group. However, in general, for the sake of beauty and tidiness, H – and – Oh are written at the same time or not at the same time.
④ Peptide sequence 3: gtflvrcdma-nh2, which differs from peptide sequence 1 in that there is more – NH2 on the right, representing C-terminal amidation.
⑤ Polypeptide sequence 4: ac-gtflvrcdma, which is different from peptide sequence 1 in that the left multi AC represents N-terminal acetylation.
Three letter writing of polypeptide
As the name suggests, three letters represent an amino acid, and the three letters are one-to-one corresponding to the single letter mentioned above. Among the three letters, Di is a capital letter, and the last two letters are small.
For example, alanine is represented by ala and cysteine is represented by Cys. For example, the three letters of peptide sequence 1 are h-gly-thr-phe-leu-val-cys-asp-met-ala-oh
② The corresponding three letters of peptide sequence 3 are: h-gly-thr-phe-leu-val-cys-asp-met-ala-nh2, C-terminal amidation.
③ The three letters corresponding to peptide sequence 4 are: AC Gly thr Phe Leu Val Cys ASP met ala Oh, which represents N-terminal acetylation.
Writing of te specific peptide sequence
For example, the writing of phosphorylated amino acids,
①：H-Gly-pThr-Phe-Leu-Val-Cys-Asp-Met-Ala-OH
②：H-Gly-Thr(PO3H2)-Phe-Leu-Val-Cys-Asp-Met-Ala-OH
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