In long polypeptide chains, N-Terminal is the amino acid end of a peptide chain, while C-Terminal is the carboxyl end. Identification is possible by tagging different sequence tags which are specific for each terminus.

Amino acids are the building blocks of protein. Proteins are naturally synthesized starting from the N-terminus and ending at the C-terminus. Thus a polypeptide would have an unbound amine group (N-terminus) at one end and unbound carboxyl group (C-terminus) at the other.

In order to ease purification following recombinant expression, proteins can be labeled with polyhistidine residues [usually 6] at either the N- or C- terminus for affinity purification. The position of the tags depends on the protein in question [e.g. if you have a (-ve) signal sequence at the N-terminus, attaching the His tag which is +vely charged (depending on pH) may distort the charge distribution thereby affecting the protein function] as this could affect protein behavior including its affinity to bind metal ions. The effect may not be unconnected with charge distribution as well as the pH.

Dear Zewdu Seyoum Tarekegn

Pls. find the attached files

https://www.researchgate.net/publication/260253429_Expression_and_Purification_of_Splicing_Proteins_from_Mammalian_Cells/figures?lo=1 in: Expression and Purification of Splicing Proteins from Mammalian Cells Article· Feb 2014 · Methods in molecular biology (Clifton, N.J.)

https://www.researchgate.net/publication/260253429_Expression_and_Purification_of_Splicing_Proteins_from_Mammalian_Cells

https://www.biocat.com/products/49002-1-LU

https://www.researchgate.net/publication/235778486_Using_Haloarcula_marismortui_Bacteriorhodopsin_as_a_Fusion_Tag_for_Enhancing_and_Visible_Expression_of_Integral_Membrane_Proteins_in_Escherichia_coli

https://www.ncbi.nlm.nih.gov/pubmed/12135367

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2909483/

http://web.mit.edu/dvp/Public/euj72wc9a8l23dtu.pdf

https://bmcbiochem.biomedcentral.com/articles/10.1186/1471-2091-14-28

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC136915/

http://pubs.acs.org/doi/abs/10.1021/bi025927l

http://www.nature.com/nbt/journal/v22/n12/full/nbt1037.html

https://www.researchgate.net/post/Where_to_place_the_tag_in_a_protein

http://www.scielo.br/scielo.php?pid=S0100-879X2004000800001&script=sci_arttext

https://www.ncbi.nlm.nih.gov/pubmed/10092499

https://www.neb.com/applications/protein-expression-and-purification/coupled-protein-expression-and-purification/tagged-protein-expression

https://en.wikipedia.org/wiki/Polyhistidine-tag

Hoping this will be helpful

Regards

Prof. Houda Kawas

Article Expression and Purification of Splicing Proteins from Mammalian Cells

Article Using Haloarcula marismortui Bacteriorhodopsin as a Fusion T...

All my friends 

I thank you very much for your information.

you most welcome

Houda

His-Tag sequence can be placed on the N- or C-terminal of a target protein by using vectors from various commercial molecular biology companies.