title: Clitocypin, a new type of cysteine proteinase inhibitor from fruit bodies of mushroom clitocybe nebularis.
abstract: A novel inhibitor of cysteine proteinases has been isolated from fruit bodies of a mushroom Clitocybe nebularis. The inhibitor was purified to homogeneity by affinity chromatography and gel filtration, followed by reverse-phase high pressure liquid chromatography. The active inhibitor has an apparent molecular mass of about 34 kDa by gel filtration and by SDS-polyacrylamide gel electrophoresis without prior boiling of the sample. Boiling in 2.5% SDS or incubation in 6 m guanidine hydrochloride resulted in a single band of 17 kDa, indicating homodimer composition with no intersubunit disulfide bonds. The inhibitor in nondenaturing buffer is resistant to boiling in water, retaining its activity and dimer composition. The mushroom protein is a tight binding inhibitor of papain (K(i) = 0.59 nm), cathepsin L (K(i) = 0.41 nm), cathepsin B (K(i) = 0.48 micrometer), and bromelain (K(i) = 0.16 micrometer) but is inactive toward cathepsin H, trypsin, and pepsin. Its isoelectric point is 4.4, and sugar analysis indicates the absence of carbohydrate. A single protein sequence of 150 amino acids, containing no cysteine or methionine residues, was obtained by amino acid sequencing. The calculated molecular mass of 16854 Da corresponds well with the value obtained by mass spectrometry. A major part of this sequence was verified by molecular cloning. The monomer sequence is clearly devoid of typical cystatin structure elements and has no similarity to any other known cysteine proteinase inhibitors but bears some similarity to a lectin-like family of proteins from mushrooms. The inhibitor, which is present in at least two other members of the Clitocybe genus, has been named clitocypin (Clitocybe cysteine proteinase inhibitor).
authors.affiliation: Department of Biochemistry and Molecular Biology, Jozef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia. joze.brzin@ijs.si
authors.forename: J
authors.initials: J
authors.lastname: Brzin
authors.forename: B
authors.initials: B
authors.lastname: Rogelj
authors.forename: T
authors.initials: T
authors.lastname: Popovic
authors.forename: B
authors.initials: B
authors.lastname: Strukelj
authors.forename: A
authors.initials: A
authors.lastname: Ritonja
mesh_terms: D000364:Agaricus / Q000737:chemistry; D000595:Amino Acid Sequence; D001483:Base Sequence; D002851:Chromatography, High Pressure Liquid; D015853:Cysteine Proteinase Inhibitors / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology*; D018076:DNA, Complementary / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology*; D006388:Hemagglutinins / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007525:Isoelectric Focusing; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D012313:RNA / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013696:Temperature
chemical_list: C411656:Clitocypin protein, Clitocybe nebularis; D015853:Cysteine Proteinase Inhibitors; D018076:DNA, Complementary; D005656:Fungal Proteins; D006388:Hemagglutinins; D012313:RNA