Immunoglobulin (Ig) domains (also called Ig folds) occur as repeating structural units in many molecules, including antibodies, the T cell antigen receptor, cytokine receptors (e.g. the platelet-derived growth factor receptor with 5 Ig domains), cell adhesion molecules (e.g. ICAM-1/CD54), and many others.

Each Ig domain consists of seven antiparallel beta strands, arranged in two sheets of four and three strands respectively. The two sheets are covalently linked with a single disulphide bond (shown here as a yellow rod). This cartoon representation is colored with RasMol's group color scheme, which makes the N/amino terminus blue, and the C/carboxy terminus red, with a spectral color sequence between these ends.

Technical Information The above animated GIF was created with the GIF Construction Set shareware from Alchemy Mindworks, Inc..