C-terminus

The C-terminus (also known as the carboxyl-terminus, carboxy-terminus, C-terminal tail, carboxy tail, C-terminal end, or COOH-terminus) is the end of an amino acid chain (protein or polypeptide), terminated by a free carboxyl group (-COOH).

The most common ER retention signal is the amino acid sequence -KDEL (Lys-Asp-Glu-Leu) or -HDEL (His-Asp-Glu-Leu) at the C-terminus.

During prenylation, a farnesyl- or geranylgeranyl-isoprenoid membrane anchor is added to a cysteine residue near the C-terminus.

[citation needed] Another form of C-terminal modification is the addition of a phosphoglycan, glycosylphosphatidylinositol (GPI), as a membrane anchor.

In humans, the CTD of RNA polymerase II typically consists of up to 52 repeats of the sequence Tyr-Ser-Pro-Thr-Ser-Pro-Ser.

A tetrapeptide (example: Val - Gly - Ser - Ala ) with green highlighted N -terminal α-amino acid (example: L- valine ) and blue marked C -terminal α-amino acid (example: L- alanine ).
RNA POL II in action.