title: A phytopathogenic cysteine peptidase from latex of wild rubber vine Cryptostegia grandiflora.
abstract: A 24,118 Da (MALDI-TOF) cysteine peptidase (EC 3.4.22.16) was purified from the latex extract of Cryptostegia grandiflora by two chromatographic steps involving ion exchange and Reverse-phase HPLC. The purified protein (Cg24-I) exhibits a single band profile following reduced SDS-PAGE and a unique amino terminal sequence, 1VPASIDWREKGTVL14, that is similar to other plant cysteine peptidases. Cg24-I displayed optimal proteolytic activity at pH 8.0 with 25 mM phosphate buffer. The proteolytic activity was inhibited with 0.2 mM E-64 and 1 mM iodoacetamide and was stimulated with 1 mM DTT. Cg24-I fully inhibited spore germination of phytopathogenic fungi Fusarium solani at a dose of 28.1 μg/mL. Its toxicity involves the membrane permeabilization of spores as probed by propidium iodide uptake. These results show that latex peptidases are part of the plant's defensive strategy against phytopathogens and that they most likely act synergistically with other recognized defensive proteins.
authors.affiliation: Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará, Campus do Pici, Cx. Postal 6033, Fortaleza, CE, CEP 60451-970, Brazil, r_marcio@hotmail.com.
authors.forename: M V
authors.initials: MV
authors.lastname: Ramos
authors.forename: D P
authors.initials: DP
authors.lastname: Souza
authors.forename: M T R
authors.initials: MT
authors.lastname: Gomes
authors.forename: C D T
authors.initials: CD
authors.lastname: Freitas
authors.forename: C P S
authors.initials: CP
authors.lastname: Carvalho
authors.forename: P A V R
authors.initials: PA
authors.lastname: Júnior
authors.forename: C E
authors.initials: CE
authors.lastname: Salas
mesh_terms: D000595:Amino Acid Sequence; D000935:Antifungal Agents / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D029062:Apocynaceae / Q000737:chemistry / Q000201:enzymology* / Q000382:microbiology*; D003546:Cysteine Endopeptidases / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D060585:Fusariosis / Q000382:microbiology / Q000517:prevention & control; D005670:Fusarium / Q000187:drug effects / Q000254:growth & development; D008969:Molecular Sequence Data; D010935:Plant Diseases / Q000382:microbiology / Q000517:prevention & control; D010936:Plant Extracts / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D059748:Proteolysis
chemical_list: D000935:Antifungal Agents; D010936:Plant Extracts; D003546:Cysteine Endopeptidases