title: Solution structure of marinostatin, a natural ester-linked protein protease inhibitor.
abstract: Marinostatin is a unique protein protease inhibitor containing two ester linkages. We have purified a 12-residue marinostatin [MST(1-12), (1)FATMRYPSDSDE(12)] and determined the residues involved in the formation of the ester linkages and the solution structure by (1)H NMR spectroscopy and restrained molecular dynamics calculation. The two ester linkages of MST(1-12) are formed between hydroxyl and carboxyl groups, Thr(3)-Asp(9) and Ser(8)-Asp(11), indicating that MST(1-12) has two cyclic regions which are fused at the residues of Ser(8) and Asp(9). A strong NOE cross-peak between Tyr(6) H(alpha) and Pro(7) H(alpha) was observed, indicating that the Pro(7) residue takes a cis-conformation. Well-converged structures and hydrogen-deuterium experiments of MST(1-12) showed that the backbone NH proton of the P1'residue, Arg(5), is hydrogen-bonded to the carbonyl oxygen of the ester linkage between Thr(3) and Asp(9). To reveal the significance of the ester linkages, a marinostatin analogue, MST-2SS ((1)FACMRYPCCSCE(12)) with two disulfide bridges of Cys(3)-Cys(9) and Cys(8)-Cys(11), was also synthesized. The inhibitory activity of MST-2SS was as strong as that of MST(1-12), and the Pro(7) residue of MST-2SS also takes a cis-conformation. However, the exchange rate of the Arg(5) NH proton of MST-2SS was about 100 times faster than that of MST(1-12), and the structure calculation of MST-2SS was not converged on account of the small number of NOEs, indicating that MST-2SS takes a more flexible structure. The hydrogen acceptability of the ester linkage formed by the P2 position residue, Thr(3), is crucial for suppressing the fluctuation of the reactive site and sustaining the inhibitory activity, which enables marinostatin to be one of the smallest protease inhibitors in nature.
authors.affiliation: Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Kanaori
authors.forename: Kaeko
authors.initials: K
authors.lastname: Kamei
authors.forename: Mai
authors.initials: M
authors.lastname: Taniguchi
authors.forename: Takao
authors.initials: T
authors.lastname: Koyama
authors.forename: Tomoharu
authors.initials: T
authors.lastname: Yasui
authors.forename: Ryo
authors.initials: R
authors.lastname: Takano
authors.forename: Chiaki
authors.initials: C
authors.lastname: Imada
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Tajima
authors.forename: Saburo
authors.initials: S
authors.lastname: Hara
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000138:chemical synthesis / Q000737:chemistry* / Q000302:isolation & purification; D001426:Bacterial Proteins / Q000138:chemical synthesis / Q000737:chemistry* / Q000302:isolation & purification; D018360:Crystallography, X-Ray; D041961:Deuterium Exchange Measurement; D004220:Disulfides / Q000737:chemistry; D004952:Esters; D019906:Nuclear Magnetic Resonance, Biomolecular; D011480:Protease Inhibitors / Q000737:chemistry*; D011487:Protein Conformation; D011498:Protein Precursors / Q000138:chemical synthesis / Q000737:chemistry* / Q000302:isolation & purification; D015842:Serine Proteinase Inhibitors / Q000737:chemistry; D012996:Solutions; D020860:Subtilisin / Q000037:antagonists & inhibitors
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D004220:Disulfides; D004952:Esters; D011480:Protease Inhibitors; D011498:Protein Precursors; D015842:Serine Proteinase Inhibitors; D012996:Solutions; C117587:marinostatin L protein, Alteromonas; D020860:Subtilisin