title: Involvement of the NH2-terminal region of oryzacystatin-I in cysteine proteinase inhibition.
abstract: Cystatins are small protein inhibitors of cysteine proteinases. The relative importance of the N-terminal region of cystatins, and of a conserved glycine within this region, remains unclear despite several studies. It was found that deletion of the N-terminal 21 amino acids abolishes the inhibitory capacity of oryzacystatin-I. The importance of a conserved glycine residue (Gly10) was also examined by replacing it with 11 other amino acids. Three further glycine residues (Gly5, -6 and -11) in this N-terminal region of oryzacystatin-I were similarly mutated. Only those variants in which Gly10 was substituted show any significant change in inhibitory capacity compared with wild-type oryzacystatin-I. The inhibitory characteristics of hybrid cystatin molecules comprising regions of chicken egg white cystatin and oryzacystatin were also examined. It is suggested that in common with animal cystatins, the N-terminal region of the plant cystatin, oryzacystatin-I, and in particular the highly conserved Gly10 residue are important for effective inhibition of papain.
authors.affiliation: Centre for Plant Biochemistry and Biotechnology, University of Leeds, UK.
authors.forename: P E
authors.initials: PE
authors.lastname: Urwin
authors.forename: H J
authors.initials: HJ
authors.lastname: Atkinson
authors.forename: M J
authors.initials: MJ
authors.lastname: McPherson
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D017124:Conserved Sequence / Q000235:genetics; D015891:Cystatins / Q000737:chemistry* / Q000494:pharmacology; D015853:Cysteine Proteinase Inhibitors / Q000737:chemistry* / Q000494:pharmacology; D017931:DNA Primers / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000235:genetics; D005998:Glycine / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010206:Papain / Q000037:antagonists & inhibitors; D015202:Protein Engineering; D017384:Sequence Deletion / Q000235:genetics
chemical_list: D015891:Cystatins; D015853:Cysteine Proteinase Inhibitors; D017931:DNA Primers; D010206:Papain; D005998:Glycine