Complement component 5 is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respon ...

that in humans is encoded by the ''C5''

gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...

. Complement component 5 is involved in the

complement system The complement system, also known as complement cascade, is a part of the immune system that enhances (complements) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promote inflammation, and ...

. It is cleaved into C5a and C5b: * C5a plays an important role in chemotaxis. * C5b forms the first part of the

complement membrane attack complex The membrane attack complex (MAC) or terminal complement complex (TCC) is a complex of proteins typically formed on the surface of pathogen cell membranes as a result of the activation of the host's complement system, and as such is an effector ...

. Deficiency is thought to cause Leiner's disease.

Function

Complement component 5 is the fifth component of complement, which plays an important role in inflammatory and cell killing processes. This protein is composed of alpha and beta polypeptide chains that are linked by a disulfide bridge. An activation peptide, C5a, which is an

anaphylatoxin Anaphylatoxins, or complement peptides, are fragments ( C3a, C4a and C5a) that are produced as part of the activation of the complement system. Complement components C3, C4 and C5 are large glycoproteins that have important functions in the immun ...

that possesses potent

spasm A spasm is a sudden involuntary contraction of a muscle, a group of muscles, or a hollow organ such as the bladder. A spasmodic muscle contraction may be caused by many medical conditions, including dystonia. Most commonly, it is a muscle ...

ogenic and