title: X-ray structures of five renin inhibitors bound to saccharopepsin: exploration of active-site specificity.
abstract: Saccharopepsin is a vacuolar aspartic proteinase involved in activation of a number of hydrolases. The enzyme has great structural homology to mammalian aspartic proteinases including human renin and we have used it as a model system to study the binding of renin inhibitors by X-ray crystallography. Five medium-to-high resolution structures of saccharopepsin complexed with transition-state analogue renin inhibitors were determined. The structure of a cyclic peptide inhibitor (PD-129,541) complexed with the proteinase was solved to 2.5 A resolution. This inhibitor has low affinity for human renin yet binds very tightly to the yeast proteinase (K(i)=4 nM). The high affinity of this inhibitor can be attributed to its bulky cyclic moiety spanning P(2)-P(3)' and other residues that appear to optimally fit the binding sub-sites of the enzyme. Superposition of the saccharopepsin structure on that of renin showed that a movement of the loop 286-301 relative to renin facilitates tighter binding of this inhibitor to saccharopepsin. Our 2.8 A resolution structure of the complex with CP-108,420 shows that its benzimidazole P(3 )replacement retains one of the standard hydrogen bonds that normally involve the inhibitor's main-chain. This suggests a non-peptide lead in overcoming the problem of susceptible peptide bonds in the design of aspartic proteinase inhibitors. CP-72,647 which possesses a basic histidine residue at P(2), has a high affinity for renin (K(i)=5 nM) but proves to be a poor inhibitor for saccharopepsin (K(i)=3.7 microM). This may stem from the fact that the histidine residue would not bind favourably with the predominantly hydrophobic S(2) sub-site of saccharopepsin.
authors.affiliation: Department of Crystallography, Birkbeck College, University of London, London, WC1E 7HX, UK.
authors.forename: N B
authors.initials: NB
authors.lastname: Cronin
authors.forename: M O
authors.initials: MO
authors.lastname: Badasso
authors.forename: I
authors.initials: I
authors.lastname: J Tickle
authors.forename: T
authors.initials: T
authors.lastname: Dreyer
authors.forename: D J
authors.initials: DJ
authors.lastname: Hoover
authors.forename: R L
authors.initials: RL
authors.lastname: Rosati
authors.forename: C C
authors.initials: CC
authors.lastname: Humblet
authors.forename: E A
authors.initials: EA
authors.lastname: Lunney
authors.forename: J B
authors.initials: JB
authors.lastname: Cooper
mesh_terms: D016282:Aspartic Acid Endopeptidases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D018360:Crystallography, X-Ray; D006801:Humans; D006860:Hydrogen Bonding; D007700:Kinetics; D008958:Models, Molecular; D009842:Oligopeptides / Q000737:chemistry* / Q000378:metabolism* / Q000494:pharmacology; D011480:Protease Inhibitors / Q000737:chemistry* / Q000378:metabolism* / Q000494:pharmacology; D017433:Protein Structure, Secondary; D012441:Saccharomyces cerevisiae / Q000737:chemistry; D029701:Saccharomyces cerevisiae Proteins; D055672:Static Electricity; D013379:Substrate Specificity; D013816:Thermodynamics; D000092502:Renin Inhibitors
chemical_list: D016282:Aspartic Acid Endopeptidases; D009842:Oligopeptides; D011480:Protease Inhibitors; D029701:Saccharomyces cerevisiae Proteins; D000092502:Renin Inhibitors; C027509:renin inhibitory peptide; C022325:aspartic proteinase A; C499266:YPS1 protein, S cerevisiae