title: Proteinase inhibitors from desert locust, Schistocerca gregaria: engineering of both P(1) and P(1)' residues converts a potent chymotrypsin inhibitor to a potent trypsin inhibitor.
abstract: Two peptides, SGCI and SGTI, that inhibited chymotrypsin and trypsin, respectively, were isolated from the haemolymph of Schistocerca gregaria. Their primary structures were found to be identical with SGP-2 and SGP-1, two of a series of peptides isolated from ovaries of the same species (A. Hamdaoui et al., FEBS Lett. 422 (1998) 74-78). All these peptides are composed of 35-36 amino acid residues and contain three homologous disulfide bridges. The residues imparting specificity to SGCI and SGTI were identified as Leu-30 and Arg-29, respectively. The peptides were synthesised by solid-phase peptide synthesis, and the synthetic ones displayed the same inhibition as the natural forms: SGCI is a strong inhibitor of chymotrypsin (K(i) = 6.2 x 10(-12) M), and SGTI is a rather weak inhibitor of trypsin (K(i) = 2.1 x 10(-7) M). The replacement of P(1) then P(1)' residues of SGCI with trypsin-specific residues increased affinity towards trypsin 3600- and 1100-fold, respectively, thus SGCI was converted to a strong trypsin inhibitor (K(i) = 5.0 x 10(-12) M) that retained some inhibitory affinity towards chymotrypsin (K(i) = 3.5 x 10(-8) M). The documented role of both P(1) and P(1)' highlights the importance of S(1)'P(1)' interactions in enzyme-inhibitor complexes.
authors.affiliation: Department of Biochemistry, Eötvös University, Puskin u.3., H-1088, Budapest, Hungary.
authors.forename: Z
authors.initials: Z
authors.lastname: Malik
authors.forename: S
authors.initials: S
authors.lastname: Amir
authors.forename: G
authors.initials: G
authors.lastname: Pál
authors.forename: Z
authors.initials: Z
authors.lastname: Buzás
authors.forename: E
authors.initials: E
authors.lastname: Várallyay
authors.forename: J
authors.initials: J
authors.lastname: Antal
authors.forename: Z
authors.initials: Z
authors.lastname: Szilágyi
authors.forename: K
authors.initials: K
authors.lastname: Vékey
authors.forename: B
authors.initials: B
authors.lastname: Asbóth
authors.forename: A
authors.initials: A
authors.lastname: Patthy
authors.forename: L
authors.initials: L
authors.lastname: Gráf
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002918:Chymotrypsin / Q000037:antagonists & inhibitors*; D051152:Clusterin; D006023:Glycoproteins / Q000737:chemistry; D006110:Grasshoppers / Q000737:chemistry*; D006458:Hemolymph / Q000737:chemistry; D019476:Insect Proteins / Q000737:chemistry* / Q000302:isolation & purification; D018832:Molecular Chaperones; D008969:Molecular Sequence Data; D011480:Protease Inhibitors / Q000737:chemistry* / Q000302:isolation & purification; D015202:Protein Engineering; D049231:Saposins; D014361:Trypsin Inhibitors / Q000737:chemistry
chemical_list: D051152:Clusterin; D006023:Glycoproteins; D019476:Insect Proteins; D018832:Molecular Chaperones; D011480:Protease Inhibitors; D049231:Saposins; D014361:Trypsin Inhibitors; D002918:Chymotrypsin