Carboxy terminal extended phytocystatins are bifunctional inhibitors of papain and legumain cysteine proteinases.
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.
Martinez
Manuel
M
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
Diaz-Mendoza
Mercedes
M
Carrillo
Laura
L
Diaz
Isabel
I
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
D015891:Cystatins; D003546:Cysteine Endopeptidases; D015853:Cysteine Proteinase Inhibitors; D010206:Papain; D010940:Plant Proteins; D000099240:Asparaginyl Endopeptidase