Collagen proteins (products of the COL gene family) are fibrous, extracellular matrix proteins with high tensile strength and are the major components of connective tissue such as tendons and cartilage. All collagens contain a triple helix domain and frequently show lateral self-association in order to form complex connective tissues. The Collagen Type XXV precursor produces the proteolytic fragment CLAC (collagenous Alzheimer amyloid plaque component), which deposits in senile plaques associated with amyloid beta peptides (Abeta) in the brains of patients with Alzheimer's disease. CLAC binds to the fibrillized form of Abeta, which disturbs the structure and function of plasma membranes.