THE RACE-SPECIFIC ELICITOR AVR9 OF THE TOMATO PATHOGEN CLADOSPORIUM-FULVUM - A CYSTINE KNOT PROTEIN - SEQUENCE-SPECIFIC H-1-NMR ASSIGNMENTS, SECONDARY STRUCTURE AND GLOBAL FOLD OF THE PROTEIN

The secondary structure and global fold of the AVR9 elicitor protein o f Cladosporium fulvum has been determined by 2D NMR and distance-geome try protocols. The protein consists of three anti-parallel strands for ming a rigid region of beta-sheet, On the basis of the NMR-derived par ameters and distance geometry calculations, it is evident that the AVR 9 protein is structurally very homologuous to carboxy peptidase inhibi tor (CPI) of which the X-ray structure is known, The AVR9 protein reve als the presence of a cystine knot, which consists of a ring formed by two disulfide bridges and the interconnecting backbone through which the third disulfide bridge penetrates. This structural motif is found in several small proteins such as proteinase inhibitors, ion channel b lockers and growth factors, The implications of the structural relatio nship between AVR9 and other biologically active proteins are discusse d. (C) 1997 Federation of European Biochemical Societies.