title: A thermostable cysteine protease precursor from a tropical plant contains an unusual C-terminal propeptide: cDNA cloning, sequence comparison and molecular modeling studies.
abstract: We report here the cloning and characterization of the entire cDNA of a papain-like cysteine protease from a tropical flowering plant. The 1098-bp ORF of the cDNA codify a protease precursor having a signal peptide of 19 amino acids, a cathepsin-L like N-terminal proregion of 114 amino acids, a mature enzyme part of 208 amino acids and a C-terminal proregion of 24 amino acids. The derived amino acid sequence of the mature part tallies with the thermostable cysteine protease Ervatamin-C--as was aimed at. The C-terminal proregion of the protease has altogether a different sequence pattern not observed in other members of the family and it contains a negatively charged helical zone. The three-dimensional model of the precursor, based on the homology modeling and X-ray structure, shows that the extended peptide stretch region of the N-terminal propeptide, covering the interdomain cleft, contains protruding side chains of positively charged residues. This study also indicates that the negatively charged zone of C-terminal propeptide may interact with the positively charged zone of the N-terminal propeptide in a cooperative manner in the maturation process of this enzyme.
authors.affiliation: Crystallography and Molecular Biology Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700 064, India.
authors.forename: Raka
authors.initials: R
authors.lastname: Ghosh
authors.forename: Jiban K
authors.initials: JK
authors.lastname: Dattagupta
authors.forename: Sampa
authors.initials: S
authors.lastname: Biswas
mesh_terms: D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D003198:Computer Simulation; D003546:Cysteine Endopeptidases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure*; D018076:DNA, Complementary / Q000235:genetics; D004795:Enzyme Stability; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D011487:Protein Conformation; D020539:Sequence Analysis, Protein; D012689:Sequence Homology, Nucleic Acid; D030014:Tabernaemontana / Q000235:genetics / Q000378:metabolism*; D013696:Temperature
chemical_list: D018076:DNA, Complementary; D007527:Isoenzymes; D010940:Plant Proteins; D003546:Cysteine Endopeptidases; C486917:ervatamin C, Ervatamia coronaria