title: Carboxy terminal extended phytocystatins are bifunctional inhibitors of papain and legumain cysteine proteinases.
abstract: Plant legumains are cysteine proteinases putatively involved in processing endogenous proteins. Phytocystatins (PhyCys) have been described as plant inhibitors of papain-like cysteine proteinases. Some PhyCys contain a carboxy terminal extension with an amino acid motif (SNSL) similar to that involved in the inhibition of legumain-like proteins by human cystatins. The role of these carboxy terminal extended PhyCys as inhibitors of legumain-like cysteine proteinases is here shown by in vitro inhibition of human legumain and legumain-like activities from barley extracts. Moreover, site-directed mutagenesis has demonstrated that the asparagine of the SNSL motif is essential in this inhibition. We prove for first time the existence of legumain inhibitors in plants.
authors.affiliation: Laboratorio de Bioquímica y Biología Molecular, Departamento de Biotecnología, Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid, ETS Ingenieros Agrónomos, Madrid, Spain. m.martinez@upm.es
authors.forename: Manuel
authors.initials: M
authors.lastname: Martinez
authors.forename: Mercedes
authors.initials: M
authors.lastname: Diaz-Mendoza
authors.forename: Laura
authors.initials: L
authors.lastname: Carrillo
authors.forename: Isabel
authors.initials: I
authors.lastname: Diaz
mesh_terms: D000595:Amino Acid Sequence; D015891:Cystatins / Q000737:chemistry* / Q000502:physiology*; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000737:chemistry / Q000502:physiology; D001467:Hordeum; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010206:Papain / Q000037:antagonists & inhibitors*; D010940:Plant Proteins / Q000737:chemistry / Q000494:pharmacology; D017434:Protein Structure, Tertiary / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D000099240:Asparaginyl Endopeptidase
chemical_list: D015891:Cystatins; D003546:Cysteine Endopeptidases; D015853:Cysteine Proteinase Inhibitors; D010206:Papain; D010940:Plant Proteins; D000099240:Asparaginyl Endopeptidase