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Lee GM, Balouch E, Goetz DH, Lazic A, McKerrow JH, Craik CS. Mapping inhibitor binding modes on an active cysteine protease via nuclear magnetic resonance spectroscopy. Biochemistry 2012. [PMID: 23181936 DOI: 10.1021/bi301305k] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Cruzain is a member of the papain/cathepsin L family of cysteine proteases, and the major cysteine protease of the protozoan Trypanosoma cruzi, the causative agent of Chagas disease. We report an autoinduction methodology that provides soluble cruzain in high yields (>30 mg/L in minimal medium). These increased yields provide sufficient quantities of active enzyme for use in nuclear magnetic resonance (NMR)-based ligand mapping. Using circular dichroism and NMR spectroscopy, we also examined the solution-state structural dynamics of the enzyme in complex with a covalently bound vinyl sulfone inhibitor (K777). We report the backbone amide and side chain carbon chemical shift assignments of cruzain in complex with K777. These resonance assignments were used to identify and map residues located in the substrate binding pocket, including the catalytic Cys25 and His162. Selective [(15)N]Cys, [(15)N]His, and [(13)C]Met labeling was performed to quickly assess cruzain-ligand interactions for a set of eight low-molecular weight compounds exhibiting micromolar binding or inhibition. Chemical shift perturbation mapping verified that six of the eight compounds bind to cruzain at the active site. Three different binding modes were delineated for the compounds, namely, covalent, noncovalent, and noninteracting. These results provide examples of how NMR spectroscopy can be used to screen compounds for fast evaluation of enzyme-inhibitor interactions to facilitate lead compound identification and subsequent structural studies.
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Affiliation(s)
- Gregory M Lee
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94158-2280, USA
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2
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Schneider EL, Lee MS, Baharuddin A, Goetz DH, Farady CJ, Ward M, Wang CI, Craik CS. A reverse binding motif that contributes to specific protease inhibition by antibodies. J Mol Biol 2011; 415:699-715. [PMID: 22154938 DOI: 10.1016/j.jmb.2011.11.036] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Revised: 11/12/2011] [Accepted: 11/18/2011] [Indexed: 10/14/2022]
Abstract
The type II transmembrane serine protease family consists of 18 closely related serine proteases that are implicated in multiple functions. To identify selective, inhibitory antibodies against one particular type II transmembrane serine protease, matriptase [MT-SP1 (membrane-type serine protease 1)], a phage display library was created with a natural repertoire of Fabs [fragment antigen binding (Fab)] from human naïve B cells. Fab A11 was identified with a 720 pM inhibition constant and high specificity for matriptase over other trypsin-fold serine proteases. A Trichoderma reesei system expressed A11 with a yield of ∼200 mg/L. The crystal structure of A11 in complex with matriptase has been determined and compared to the crystal structure of another antibody inhibitor (S4) in complex with matriptase. Previously discovered from a synthetic single-chain variable fragment library, S4 is also a highly selective and potent matriptase inhibitor. The crystal structures of the A11/matriptase and S4/matriptase complexes were solved to 2.1 Å and 1.5 Å, respectively. Although these antibodies, discovered from separate libraries, interact differently with the protease surface loops for their specificity, the structures reveal a similar novel mechanism of protease inhibition. Through the insertion of the H3 variable loop in a reverse orientation at the substrate-binding pocket, these antibodies bury a large surface area for potent inhibition and avoid proteolytic inactivation. This discovery highlights the critical role that the antibody scaffold plays in positioning loops to bind and inhibit protease function in a highly selective manner. Additionally, Fab A11 is a fully human antibody that specifically inhibits matriptase over other closely related proteases, suggesting that this approach could be useful for clinical applications.
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Affiliation(s)
- Eric L Schneider
- Department of Pharmaceutical Chemistry, University of California, San Francisco, Genentech Hall, San Francisco, CA 94143-2280, USA
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3
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Zhou Y, Agudelo J, Lu K, Goetz DH, Hansell E, Chen YT, Roush WR, McKerrow J, Craik CS, Amberg SM, Simmons G. Inhibitors of SARS-CoV entry--identification using an internally-controlled dual envelope pseudovirion assay. Antiviral Res 2011; 92:187-94. [PMID: 21820471 PMCID: PMC3205982 DOI: 10.1016/j.antiviral.2011.07.016] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Revised: 07/13/2011] [Accepted: 07/19/2011] [Indexed: 12/30/2022]
Abstract
Severe acute respiratory syndrome-associated coronavirus (SARS-CoV) emerged as the causal agent of an endemic atypical pneumonia, infecting thousands of people worldwide. Although a number of promising potential vaccines and therapeutic agents for SARS-CoV have been described, no effective antiviral drug against SARS-CoV is currently available. The intricate, sequential nature of the viral entry process provides multiple valid targets for drug development. Here, we describe a rapid and safe cell-based high-throughput screening system, dual envelope pseudovirion (DEP) assay, for specifically screening inhibitors of viral entry. The assay system employs a novel dual envelope strategy, using lentiviral pseudovirions as targets whose entry is driven by the SARS-CoV Spike glycoprotein. A second, unrelated viral envelope is used as an internal control to reduce the number of false positives. As an example of the power of this assay a class of inhibitors is reported with the potential to inhibit SARS-CoV at two steps of the replication cycle, viral entry and particle assembly. This assay system can be easily adapted to screen entry inhibitors against other viruses with the careful selection of matching partner virus envelopes.
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Affiliation(s)
- Yanchen Zhou
- Blood Systems Research Institute, University of California, San Francisco, CA 94118, USA
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4
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Devireddy LR, Hart DO, Goetz DH, Green MR. A mammalian siderophore synthesized by an enzyme with a bacterial homolog involved in enterobactin production. Cell 2010; 141:1006-17. [PMID: 20550936 DOI: 10.1016/j.cell.2010.04.040] [Citation(s) in RCA: 228] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2009] [Revised: 02/11/2010] [Accepted: 03/23/2010] [Indexed: 11/24/2022]
Abstract
Intracellular iron homeostasis is critical for survival and proliferation. Lipocalin 24p3 is an iron-trafficking protein that binds iron through association with a bacterial siderophore, such as enterobactin, or a postulated mammalian siderophore. Here, we show that the iron-binding moiety of the 24p3-associated mammalian siderophore is 2,5-dihydroxybenzoic acid (2,5-DHBA), which is similar to 2,3-DHBA, the iron-binding component of enterobactin. We find that the murine enzyme responsible for 2,5-DHBA synthesis, BDH2, is the homolog of bacterial EntA, which catalyzes 2,3-DHBA production during enterobactin biosynthesis. RNA interference-mediated knockdown of BDH2 results in siderophore depletion. Mammalian cells lacking the siderophore accumulate abnormally high amounts of cytoplasmic iron, resulting in elevated levels of reactive oxygen species, whereas the mitochondria are iron deficient. Siderophore-depleted mammalian cells and zebrafish embryos fail to synthesize heme, an iron-dependent mitochondrial process. Our results reveal features of intracellular iron homeostasis that are conserved from bacteria through humans.
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Affiliation(s)
- Laxminarayana R Devireddy
- Case Comprehensive Cancer Center and Department of Pathology, Case Western Reserve University, Cleveland, OH 44106, USA.
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5
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Ohol YM, Goetz DH, Chan K, Shiloh MU, Craik CS, Cox JS. Mycobacterium tuberculosis MycP1 protease plays a dual role in regulation of ESX-1 secretion and virulence. Cell Host Microbe 2010; 7:210-20. [PMID: 20227664 DOI: 10.1016/j.chom.2010.02.006] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2009] [Revised: 12/05/2009] [Accepted: 02/09/2010] [Indexed: 11/19/2022]
Abstract
Mycobacterium tuberculosis uses the ESX-1 secretion system to deliver virulence proteins during infection of host cells. Here we report a mechanism of posttranscriptional control of ESX-1 mediated by MycP1, a M. tuberculosis serine protease. We show that MycP1 is required for ESX-1 secretion but that, unexpectedly, genetic inactivation of MycP1 protease activity increases secretion of ESX-1 substrates. We demonstrate that EspB, an ESX-1 substrate required for secretion, is a target of MycP1 in vitro and in vivo. During macrophage infection, an inactive MycP1 protease mutant causes hyperactivation of ESX-1-stimulated innate signaling pathways. MycP1 is required for growth in mice during acute infection, while loss of its protease activity leads to attenuated virulence during chronic infection. As the key ESX-1 substrates ESAT-6 and CFP-10 are highly immunogenic, fine-tuning of their secretion by MycP1 may balance virulence and immune detection and be essential for successful maintenance of long-term M. tuberculosis infection.
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Affiliation(s)
- Yamini M Ohol
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA 94158, USA
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6
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Duriseti S, Goetz DH, Hostetter DR, LeBeau AM, Wei Y, Craik CS. Antagonistic anti-urokinase plasminogen activator receptor (uPAR) antibodies significantly inhibit uPAR-mediated cellular signaling and migration. J Biol Chem 2010; 285:26878-26888. [PMID: 20501655 DOI: 10.1074/jbc.m109.077677] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Interactions between urokinase plasminogen activator receptor (uPAR) and its various ligands regulate tumor growth, invasion, and metastasis. Antibodies that bind specific uPAR epitopes may disrupt these interactions, thereby inhibiting these processes. Using a highly diverse and naïve human fragment of the antigen binding (Fab) phage display library, we identified 12 unique human Fabs that bind uPAR. Two of these antibodies compete against urokinase plasminogen activator (uPA) for uPAR binding, whereas a third competes with beta1 integrins for uPAR binding. These competitive antibodies inhibit uPAR-dependent cell signaling and invasion in the non-small cell lung cancer cell line, H1299. Additionally, the integrin-blocking antibody abrogates uPAR/beta1 integrin-mediated H1299 cell adhesion to fibronectin and vitronectin. This antibody and one of the uPAR/uPA antagonist antibodies shows a significant combined effect in inhibiting cell invasion through Matrigel/Collagen I or Collagen I matrices. Our results indicate that these antagonistic antibodies have potential for the detection and treatment of uPAR-expressing tumors.
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Affiliation(s)
- Sai Duriseti
- Graduate Group in Biophysics, University of California, San Francisco, California 94158-2517
| | - David H Goetz
- Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94158-2517
| | - Daniel R Hostetter
- Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94158-2517
| | - Aaron M LeBeau
- Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94158-2517
| | - Ying Wei
- Department of Medicine and Cardiovascular Research Institute, University of California, San Francisco, California 94158-2517.
| | - Charles S Craik
- Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94158-2517.
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7
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Mahon CS, O'Donoghue AJ, Goetz DH, Murray PG, Craik CS, Tuohy MG. Characterization of a multimeric, eukaryotic prolyl aminopeptidase: an inducible and highly specific intracellular peptidase from the non-pathogenic fungus Talaromyces emersonii. Microbiology (Reading) 2009; 155:3673-3682. [PMID: 19556294 DOI: 10.1099/mic.0.030940-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Fungi are capable of degrading proteins in their environment by secreting peptidases. However, the link between extracellular digestion and intracellular proteolysis has scarcely been investigated. Mycelial lysates of the filamentous fungus Talaromyces emersonii were screened for intracellular peptidase production. Five distinct proteolytic activities with specificity for the p-nitroanilide (pNA) peptides Suc-AAPF-pNA, Suc-AAA-pNA, K-pNA, F-pNA and P-pNA were identified. The native enzyme responsible for the removal of N-terminal proline residues was purified to homogeneity by ammonium sulfate fractionation followed by five successive chromatographic steps. The enzyme, termed Talaromyces emersonii prolyl aminopeptidase (TePAP), displayed a 50-fold specificity for cleaving N-terminal Pro-X (k(cat)/K(m)=2.1 x 10(6) M(-1) s(-1)) compared with Ala-X or Val-X bonds. This intracellular aminopeptidase was optimally active at pH 7.4 and 50 degrees C. Peptide sequencing facilitated the design of degenerate oligonucleotides from homologous sequences encoding putative fungal proline aminopeptidases, enabling subsequent cloning of the gene. TePAP was shown to be relatively uninhibited by classical serine peptidase inhibitors and to be sensitive to selected cysteine- and histidine-modifying reagents, yet gene sequence analysis identified the protein as a serine peptidase with an alpha/beta hydrolase fold. Northern analysis indicated that Tepap mRNA levels were regulated by the composition of the growth medium. Highest Tepap transcript levels were observed when the fungus was grown in medium containing glucose and the protein hydrolysate casitone. Interestingly, both the induction profile and substrate preference of this enzyme suggest potential co-operativity between extracellular and intracellular proteolysis in this organism. Gel filtration chromatography suggested that the enzyme exists as a 270 kDa homo-hexamer, whereas most bacterial prolyl aminopeptidases (PAPs) are monomers. Phylogenetic analysis of known PAPs revealed two diverse subfamilies that are distinguishable on the basis of primary and secondary structure and appear to correlate with the subunit composition of the native enzymes. Sequence comparisons revealed that PAPs with key conserved topological features are widespread in bacterial and fungal kingdoms, and this study identified many putative PAP candidates within sequenced genomes. This work represents, to our knowledge, the first detailed biochemical and molecular analysis of an inducible PAP from a eukaryote and the first intracellular peptidase isolated from the thermophilic fungus T. emersonii.
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Affiliation(s)
- Cathal S Mahon
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94158, USA.,Department of Biochemistry, National University of Ireland, University Road, Galway, Ireland
| | - Anthony J O'Donoghue
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94158, USA.,Department of Biochemistry, National University of Ireland, University Road, Galway, Ireland
| | - David H Goetz
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94158, USA
| | - Patrick G Murray
- Department of Biochemistry, National University of Ireland, University Road, Galway, Ireland
| | - Charles S Craik
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94158, USA
| | - Maria G Tuohy
- Department of Biochemistry, National University of Ireland, University Road, Galway, Ireland
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O'Donoghue AJ, Mahon CS, Goetz DH, O'Malley JM, Gallagher DM, Zhou M, Murray PG, Craik CS, Tuohy MG. Inhibition of a secreted glutamic peptidase prevents growth of the fungus Talaromyces emersonii. J Biol Chem 2008; 283:29186-95. [PMID: 18687686 DOI: 10.1074/jbc.m802366200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The thermophilic filamentous fungus Talaromyces emersonii secretes a variety of hydrolytic enzymes that are of interest for processing of biomass into fuel. Many carbohydrases have been isolated and characterized from this fungus, but no studies had been performed on peptidases. In this study, two acid-acting endopeptidases were isolated and characterized from the culture filtrate of T. emersonii. One of these enzymes was identified as a member of the recently classified glutamic peptidase family and was subsequently named T. emersonii glutamic peptidase 1 (TGP1). The second enzyme was identified as an aspartyl peptidase (PEP1). TGP1 was cloned and sequenced and shown to exhibit 64 and 47% protein identity to peptidases from Aspergillus niger and Scytalidium lignocolum, respectively. Substrate profiling of 16 peptides determined that TGP1 has broad specificity with a preference for large residues in the P1 site, particularly Met, Gln, Phe, Lys, Glu, and small amino acids at P1' such as Ala, Gly, Ser, or Thr. This enzyme efficiently cleaves an internally quenched fluorescent substrate containing the zymogen activation sequence (k(cat)/K(m)=2 x 10(5) m(-1) s(-1)). Maximum hydrolysis occurs at pH 3.4 and 50 degrees C. The reaction is strongly inhibited by a transition state peptide analog, TA1 (K(i)=1.5 nM), as well as a portion of the propeptide sequence, PT1 (K(i)=32 nM). Ex vivo studies show that hyphal extension of T. emersonii in complex media is unaffected by the aspartyl peptidase inhibitor pepstatin but is inhibited by TA1 and PT1. This study provides insight into the functional role of the glutamic peptidase TGP1 for growth of T. emersonii.
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Affiliation(s)
- Anthony J O'Donoghue
- Department of Biochemistry, National University of Ireland, University Road, Galway, Ireland
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9
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Lazic A, Goetz DH, Nomura AM, Marnett AB, Craik CS. Substrate modulation of enzyme activity in the herpesvirus protease family. J Mol Biol 2007; 373:913-23. [PMID: 17870089 PMCID: PMC2078331 DOI: 10.1016/j.jmb.2007.07.073] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2007] [Revised: 07/21/2007] [Accepted: 07/26/2007] [Indexed: 11/23/2022]
Abstract
The herpesvirus proteases are an example in which allosteric regulation of an enzyme activity is achieved through the formation of quaternary structure. Here, we report a 1.7 A resolution structure of Kaposi's sarcoma-associated herpesvirus protease in complex with a hexapeptide transition state analogue that stabilizes the dimeric state of the enzyme. Extended substrate binding sites are induced upon peptide binding. In particular, 104 A2 of surface are buried in the newly formed S4 pocket when tyrosine binds at this site. The peptide inhibitor also induces a rearrangement of residues that stabilizes the oxyanion hole and the dimer interface. Concomitant with the structural changes, an increase in catalytic efficiency of the enzyme results upon extended substrate binding. A nearly 20-fold increase in kcat/KM results upon extending the peptide substrate from a tetrapeptide to a hexapeptide exclusively due to a KM effect. This suggests that the mechanism by which herpesvirus proteases achieve their high specificity is by using extended substrates to modulate both the structure and activity of the enzyme.
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Affiliation(s)
- Ana Lazic
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94158-2517, USA
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10
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Goetz DH, Choe Y, Hansell E, Chen YT, McDowell M, Jonsson CB, Roush WR, McKerrow J, Craik CS. Substrate Specificity Profiling and Identification of a New Class of Inhibitor for the Major Protease of the SARS Coronavirus,. Biochemistry 2007; 46:8744-52. [PMID: 17605471 DOI: 10.1021/bi0621415] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Severe acute respiratory syndrome (SARS) is an emerging infectious disease associated with a high rate of mortality. The SARS-associated coronavirus (SARS-CoV) has been identified as the etiological agent of the disease. Although public health procedures have been effective in combating the spread of SARS, concern remains about the possibility of a recurrence. Various approaches are being pursued for the development of efficacious therapeutics. One promising approach is to develop small molecule inhibitors of the essential major polyprotein processing protease 3Clpro. Here we report a complete description of the tetrapeptide substrate specificity of 3Clpro using fully degenerate peptide libraries consisting of all 160,000 possible naturally occurring tetrapeptides. The substrate specificity data show the expected P1-Gln P2-Leu specificity and elucidate a novel preference for P1-His containing substrates equal to the expected preference for P1-Gln. These data were then used to develop optimal substrates for a high-throughput screen of a 2000 compound small-molecule inhibitor library consisting of known cysteine protease inhibitor scaffolds. We also report the 1.8 A X-ray crystal structure of 3Clpro bound to an irreversible inhibitor. This inhibitor, an alpha,beta-epoxyketone, inhibits 3Clpro with a k3/Ki of 0.002 microM(-1) s(-1) in a mode consistent with the substrate specificity data. Finally, we report the successful rational improvement of this scaffold with second generation inhibitors. These data provide the foundation for a rational small-molecule inhibitor design effort based upon the inhibitor scaffold identified, the crystal structure of the complex, and a more complete understanding of P1-P4 substrate specificity.
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Affiliation(s)
- D H Goetz
- Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94143, USA
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11
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Bell JK, Goetz DH, Mahrus S, Harris JL, Fletterick RJ, Craik CS. The oligomeric structure of human granzyme A is a determinant of its extended substrate specificity. Nat Struct Mol Biol 2003; 10:527-34. [PMID: 12819769 DOI: 10.1038/nsb944] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2003] [Accepted: 05/23/2003] [Indexed: 11/09/2022]
Abstract
The cell death-inducing serine protease granzyme A (GzmA) has a unique disulfide-linked quaternary structure. The structure of human GzmA bound to a tripeptide CMK inhibitor, determined at a resolution of 2.4 A, reveals that the oligomeric state contributes to substrate selection by limiting access to the active site for potential macromolecular substrates and inhibitors. Unlike other serine proteases, tetrapeptide substrate preferences do not correlate well with natural substrate cleavage sequences. This suggests that the context of the cleavage sequence within a macromolecular substrate imposes another level of selection not observed with the peptide substrates. Modeling of inhibitors bound to the GzmA active site shows that the dimer also contributes to substrate specificity in a unique manner by extending the active-site cleft. The crystal structure, along with substrate library profiling and mutagenesis, has allowed us to identify and rationally manipulate key components involved in GzmA substrate specificity.
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Affiliation(s)
- Jessica K Bell
- Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94143, USA
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Goetz DH, Holmes MA, Borregaard N, Bluhm ME, Raymond KN, Strong RK. The neutrophil lipocalin NGAL is a bacteriostatic agent that interferes with siderophore-mediated iron acquisition. Mol Cell 2002; 10:1033-43. [PMID: 12453412 DOI: 10.1016/s1097-2765(02)00708-6] [Citation(s) in RCA: 979] [Impact Index Per Article: 44.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
First identified as a neutrophil granule component, neutrophil gelatinase-associated lipocalin (NGAL; also called human neutrophil lipocalin, 24p3, uterocalin, or neu-related lipocalin) is a member of the lipocalin family of binding proteins. Putative NGAL ligands, including neutrophil chemotactic agents such as N-formylated tripeptides, have all been refuted by recent biochemical and structural results. NGAL has subsequently been implicated in diverse cellular processes, but without a characterized ligand, the molecular basis of these functions remained mysterious. Here we report that NGAL tightly binds bacterial catecholate-type ferric siderophores through a cyclically permuted, hybrid electrostatic/cation-pi interaction and is a potent bacteriostatic agent in iron-limiting conditions. We therefore propose that NGAL participates in the antibacterial iron depletion strategy of the innate immune system.
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Affiliation(s)
- David H Goetz
- Molecular and Cellular Biology Program, Fred Hutchinson Cancer Research Center, Box 357275, University of Washington, Seattle, WA 98105, USA
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Goetz DH, Willie ST, Armen RS, Bratt T, Borregaard N, Strong RK. Ligand preference inferred from the structure of neutrophil gelatinase associated lipocalin. Biochemistry 2000; 39:1935-41. [PMID: 10684642 DOI: 10.1021/bi992215v] [Citation(s) in RCA: 137] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Neutrophil gelatinase associated lipocalin (NGAL), a constituent of neutrophil granules, is a member of the lipocalin family of binding proteins. NGAL can also be highly induced in epithelial cells in both inflammatory and neoplastic colorectal disease. NGAL is proposed to mediate inflammatory responses by sequestering neutrophil chemoattractants, particularly N-formylated tripeptides and possibly leukotriene B(4) and platelet activating factor. The crystal structures of NGAL display a typical lipocalin fold, albeit with an unusually large and atypically polar binding site, or calyx. The fold of NGAL is most similar to the epididymal retinoic acid-binding protein, another lipocalin, though the overall architecture of the calyces are very different. The crystal structures also reveal either sulfate ions or an adventitiously copurified fatty acid bound in the binding site. Neither ligand is displaced by added N-formylated tripeptides. The size, shape, and character of the NGAL calyx, as well as the low relative affinity for N-formylated tripeptides, suggest that neither the copurified fatty acid nor any of the proposed ligands are likely to be the preferred ligand of this protein. Comparisons between the crystal structures and the recently reported solution structure of NGAL reveal significant differences, in terms of both the details of the structure and the overall flexibility of the fold.
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Affiliation(s)
- D H Goetz
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA
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Abstract
Amide-linked conjugates of indole-3-acetic acid (IAA) are putative storage or inactivation forms of the growth hormone auxin. Here, we describe the Arabidopsis iar3 mutant that displays reduced sensitivity to IAA-Ala. IAR3 is a member of a family of Arabidopsis genes related to the previously isolated ILR1 gene, which encodes an IAA-amino acid hydrolase selective for IAA-Leu and IAA-Phe. IAR3 and the very similar ILL5 gene are closely linked on chromosome 1 and comprise a subfamily of the six Arabidopsis IAA-conjugate hydrolases. The purified IAR3 enzyme hydrolyzes IAA-Ala in vitro. iar 3 ilr1 double mutants are more resistant than either single mutant to IAA-amino acid conjugates, and plants overexpressing IAR3 or ILR1 are more sensitive than is the wild type to certain IAA-amino acid conjugates, reflecting the overlapping substrate specificities of the corresponding enzymes. The IAR3 gene is expressed most strongly in roots, stems, and flowers, suggesting roles for IAA-conjugate hydrolysis in those tissues.
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Affiliation(s)
- R T Davies
- Department of Biochemistry and Cell Biology, Rice University, Houston, Texas 77005-1892, USA
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