title: The unique structure of carbonic anhydrase αCA1 from Chlamydomonas reinhardtii.
abstract: Chlamydomonas reinhardtii α-type carbonic anhydrase (Cr-αCA1) is a dimeric enzyme that catalyses the interconversion of carbon dioxide and carbonic acid. The precursor form of Cr-αCA1 undergoes post-translational cleavage and N-glycosylation. Comparison of the genomic sequences of precursor Cr-αCA1 and other αCAs shows that Cr-αCA1 contains a different N-terminal sequence and two insertion sequences. A 35-residue peptide in one of the insertion sequences is deleted from the precursor during maturation. The crystal structure of the mature form of Cr-αCA1 has been determined at 1.88 Å resolution. Each subunit is cleaved into the long and short peptides, but they are linked together by a disulfide bond. The two subunits are linked by a disulfide bond. N-Glycosylations occur at three asparagine residues and the attached N-glycans protrude into solvent regions. The subunits consist of a core β-sheet structure composed of nine β-strands. At the centre of the β-sheet is the catalytic site, which contains a Zn atom bound to three histidine residues. The amino-acid residues around the Zn atom are highly conserved in other monomeric and dimeric αCAs. The short peptide runs near the active site and forms a hydrogen bond to the zinc-coordinated residue in the long chain, suggesting an important role for the short peptide in Cr-αCA1 activity.
authors.affiliation: College of Science and Engineering, Iwaki-Meisei University, Chuodai-iino, Iwaki, Fukushima 970-8551, Japan.
authors.forename: Kaoru
authors.initials: K
authors.lastname: Suzuki
authors.forename: Shi-Yuan
authors.initials: SY
authors.lastname: Yang
authors.forename: Satoru
authors.initials: S
authors.lastname: Shimizu
authors.forename: Ella Czarina
authors.initials: EC
authors.lastname: Morishita
authors.forename: Jiandong
authors.initials: J
authors.lastname: Jiang
authors.forename: Fang
authors.initials: F
authors.lastname: Zhang
authors.forename: Md Mominul
authors.initials: MM
authors.lastname: Hoque
authors.forename: Yoshiteru
authors.initials: Y
authors.lastname: Sato
authors.forename: Masaru
authors.initials: M
authors.lastname: Tsunoda
authors.forename: Takeshi
authors.initials: T
authors.lastname: Sekiguchi
authors.forename: Akio
authors.initials: A
authors.lastname: Takénaka
mesh_terms: D000595:Amino Acid Sequence; D001216:Asparagine / Q000378:metabolism; D002256:Carbonic Anhydrases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020134:Catalytic Domain; D016825:Chlamydomonas reinhardtii / Q000201:enzymology*; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D019281:Dimerization; D004220:Disulfides / Q000737:chemistry; D006031:Glycosylation; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D015032:Zinc / Q000378:metabolism
chemical_list: D004220:Disulfides; D001216:Asparagine; D002256:Carbonic Anhydrases; D015032:Zinc