title: Crystal structure of the catalytic domain of the tumor-associated human carbonic anhydrase IX.
abstract: Carbonic anhydrase (CA) IX is a plasma membrane-associated member of the alpha-CA enzyme family, which is involved in solid tumor acidification. It is a marker of tumor hypoxia and a prognostic factor in several human cancers. An aberrant increase in CA IX expression in chronic hypoxia and during development of various carcinomas contributes to tumorigenesis through at least two mechanisms: pH regulation and cell adhesion control. Here we report the X-ray structure of the catalytic domain of CA IX in complex with a classical, clinically used sulfonamide inhibitor, acetazolamide. The structure reveals a typical alpha-CA fold, which significantly differs from the other CA isozymes when the protein quaternary structure is considered. Thus, two catalytic domains of CA IX associate to form a dimer, which is stabilized by the formation of an intermolecular disulfide bond. The active site clefts and the PG domains are located on one face of the dimer, while the C-termini are located on the opposite face to facilitate protein anchoring to the cell membrane. A correlation between the three-dimensional structure and the physiological role of the enzyme is here suggested, based on the measurement of the pH profile of the catalytic activity for the physiological reaction, CO(2) hydration to bicarbonate and protons. On the basis of the structural differences observed between CA IX and the other membrane-associated alpha-CAs, further prospects for the rational drug design of isozyme-specific CA inhibitors are proposed, given that inhibition of this enzyme shows antitumor activity both in vitro and in vivo.
authors.affiliation: Istituto di Biostrutture e Bioimmagini-CNR, via Mezzocannone 16, 80134 Naples, Italy.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Alterio
authors.forename: Mika
authors.initials: M
authors.lastname: Hilvo
authors.forename: Anna
authors.initials: A
authors.lastname: Di Fiore
authors.forename: Claudiu T
authors.initials: CT
authors.lastname: Supuran
authors.forename: Peiwen
authors.initials: P
authors.lastname: Pan
authors.forename: Seppo
authors.initials: S
authors.lastname: Parkkila
authors.forename: Andrea
authors.initials: A
authors.lastname: Scaloni
authors.forename: Jaromir
authors.initials: J
authors.lastname: Pastorek
authors.forename: Silvia
authors.initials: S
authors.lastname: Pastorekova
authors.forename: Carlo
authors.initials: C
authors.lastname: Pedone
authors.forename: Andrea
authors.initials: A
authors.lastname: Scozzafava
authors.forename: Simona Maria
authors.initials: SM
authors.lastname: Monti
authors.forename: Giuseppina
authors.initials: G
authors.lastname: De Simone
mesh_terms: D000595:Amino Acid Sequence; D000951:Antigens, Neoplasm / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001639:Bicarbonates / Q000737:chemistry / Q000378:metabolism; D002245:Carbon Dioxide / Q000737:chemistry / Q000378:metabolism; D000071231:Carbonic Anhydrase IX; D002256:Carbonic Anhydrases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D020134:Catalytic Domain; D003460:Crystallization; D018360:Crystallography, X-Ray; D004220:Disulfides / Q000737:chemistry; D015195:Drug Design; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009369:Neoplasms / Q000188:drug therapy / Q000201:enzymology* / Q000473:pathology; D011487:Protein Conformation; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D011522:Protons; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship; D014867:Water / Q000737:chemistry / Q000378:metabolism
chemical_list: D000951:Antigens, Neoplasm; D001639:Bicarbonates; D004220:Disulfides; D004791:Enzyme Inhibitors; D011522:Protons; D011994:Recombinant Proteins; D014867:Water; D002245:Carbon Dioxide; C089226:CA9 protein, human; D000071231:Carbonic Anhydrase IX; D002256:Carbonic Anhydrases