Linear Epitope

Linear Epitope

A linear or a sequential epitope is an epitope that is recognized by antibodies by its linear sequence of amino acids, or primary structure. In contrast, most antibodies recognize a conformational epitope that has a specific three-dimensional shape and its protein structure.

An antigen is any substance that the immune system can recognize as foreign. Since, antigens are usually proteins that are too large to bind as a whole to any receptor, only specific segments that form the antigen bind with a specific antibody. Such segments are called epitopes. Likewise, it is only paratope of the antibody that comes in contact with the epitope.

Proteins are composed of repeating nitrogen-containing subunits called amino acids. The linear sequence of amino acids that compose a protein is called its primary structure, which does not exist in nature. But, when an antigen is broken down in a lysosome, it yields small peptides, which can be recognized through the amino acids that lie continuously in a line, and hence are called linear epitopes.