[New molecular and clinical information about collagens].

Collagen is one of the most abundant proteins in human tissues. Together with other connective tissue components (non-collagenous glycoproteins, proteoglycans, laminins, thrombospondins, entactin and tenascin), collagen promotes cellular adhesion, activates intracellular signals, and regulates the biological activities of growth factors and other proteins. During the past 20 years at least 19 genetically different collagenous proteins coded by 30 distinct genes have been identified. Here, we review some new aspects of the collagens that form fibrils, sheets, or beaded filaments, and of the so-called multiplexin collagens. Whenever possible, we give insights regarding the association of the structural abnormalities of these proteins as they relate with human disease(s).