carboxylterminus

The carboxylterminus, also known as the C-terminus, is the end of a peptide chain that terminates with a carboxyl group (-COOH). This is in contrast to the amino terminus, or N-terminus, which terminates with an amino group (-NH2). When amino acids link together to form a polypeptide chain, they do so through peptide bonds, forming a linear sequence. Each amino acid in the chain, except for the two at the ends, has both a free amino group and a free carboxyl group. The C-terminus specifically refers to the end of this chain where the last amino acid's carboxyl group remains unreacted by another amino acid. This terminal carboxyl group can be ionized at physiological pH, becoming a negatively charged carboxylate group (-COO-). The carboxylterminus plays a crucial role in protein structure and function. It can be involved in protein folding, interacting with other molecules, and can serve as a site for post-translational modifications. For example, some proteins are cleaved at their C-terminus, or other chemical groups can be attached there, influencing the protein's activity and stability. The directionality of the polypeptide chain, from N-terminus to C-terminus, is fundamental in understanding protein synthesis and structure.