Extensin—a major cell wall glycoprotein

Abstract The structure of extensin is described in detail. It has a hydroxyproline‐rich backbone, which contains repeating peptides glycosylated by short side chains and it adopts a polyproline II helical conformation. The glycoprotein is synthesized intracellularly and soluble precursors are secreted to the wall, where they are bound, perhaps, by the formation of isodityrosine cross‐links. The various hypotheses, including the most recent ‘warp and weft’ model, which have been suggested to explain the attachment of extensin to the other wall polymers are discussed. The possible functions of extensin in defence and in the control of extension growth are described in addition to its probable structural role. Other glycoproteins which resemble extensin are also mentioned.