title: A subtilisin inhibitor produced by Streptomyces bikiniensis possesses a glutamine residue at reactive site P1.
abstract: We determined the complete amino acid sequence of a novel subtilisin inhibitor, SIL15, which had been isolated from the culture supernatant of Streptomyces bikiniensis and shown to be a member of the Streptomyces subtilisin inhibitor (SSI)-like (SIL) protein family, and then identified its reactive site. SIL15 is composed of 113 amino acids and exists as a dimer. Compared with other SSI-family inhibitors, SIL15 was found to be unique in that it possesses a Gln residue at the P1 site of the reactive site and has two-residue insertions in two regions, one in the alpha 1-helix and the other in the flexible loop region near the reactive site. Inhibition of subtilisin BPN' by SIL15 (inhibitor constant, 2.7 x 10(-11) M) was due to the presence of a Gln residue at the P1 site, which was well consistent with the results obtained for P1-site mutants of SSI and turkey ovomucoid domain 3.
authors.affiliation: Institute for Biomolecular Science, Gakushuin University, Tokyo.
authors.forename: M
authors.initials: M
authors.lastname: Terabe
authors.forename: S
authors.initials: S
authors.lastname: Kojima
authors.forename: S
authors.initials: S
authors.lastname: Taguchi
authors.forename: H
authors.initials: H
authors.lastname: Momose
authors.forename: K
authors.initials: K
authors.lastname: Miura
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000096:biosynthesis*; D001665:Binding Sites; D005973:Glutamine / Q000737:chemistry*; D008969:Molecular Sequence Data
chemical_list: D001426:Bacterial Proteins; C018150:subtilisin inhibitor protein, Streptomyces; D005973:Glutamine