title: Crystal structure of the "cab"-type beta class carbonic anhydrase from the archaeon Methanobacterium thermoautotrophicum.
abstract: The structure of the "cab"-type beta class carbonic anhydrase from the archaeon Methanobacterium thermoautotrophicum (Cab) has been determined to 2.1-A resolution using the multiwavelength anomalous diffraction phasing technique. Cab exists as a dimer with a subunit fold similar to that observed in "plant"-type beta class carbonic anhydrases. The active site zinc is coordinated by protein ligands Cys(32), His(87), and Cys(90), with the tetrahedral coordination completed by a water molecule. The major difference between plant- and cab-type beta class carbonic anhydrases is in the organization of the hydrophobic pocket. The structure reveals a Hepes buffer molecule bound 8 A away from the active site zinc, which suggests a possible proton transfer pathway from the active site to the solvent.
authors.affiliation: Biochemistry Option, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: P
authors.initials: P
authors.lastname: Strop
authors.forename: K S
authors.initials: KS
authors.lastname: Smith
authors.forename: T M
authors.initials: TM
authors.lastname: Iverson
authors.forename: J G
authors.initials: JG
authors.lastname: Ferry
authors.forename: D C
authors.initials: DC
authors.lastname: Rees
mesh_terms: D000595:Amino Acid Sequence; D001105:Archaea / Q000201:enzymology*; D001665:Binding Sites; D002256:Carbonic Anhydrases / Q000737:chemistry*; D003461:Crystallography; D003545:Cysteine / Q000737:chemistry; D006639:Histidine / Q000737:chemistry; D007700:Kinetics; D008024:Ligands; D017014:Methanobacterium / Q000201:enzymology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011522:Protons; D017386:Sequence Homology, Amino Acid; D013050:Spectrometry, Fluorescence; D014867:Water / Q000378:metabolism; D015032:Zinc / Q000737:chemistry
chemical_list: D008024:Ligands; D011522:Protons; D014867:Water; D006639:Histidine; D002256:Carbonic Anhydrases; D015032:Zinc; D003545:Cysteine