PMID: 21931221 , Related PDB id: 3B1B

Authors:

Suzuki K, Yang SY, Shimizu S, Morishita EC, Jiang J, Zhang F, Hoque MM, Sato Y, Tsunoda M, Sekiguchi T, Takenaka A

Title:

The unique structure of carbonic anhydrase alphaCA1 from Chlamydomonas reinhardtii.

Journal:

Acta Crystallogr D Biol Crystallogr. 2011 Oct;67(Pt 10):894-901. Epub 2011 Sep 8.

Abstract:

Chlamydomonas reinhardtii alpha-type carbonic anhydrase (Cr-alphaCA1) is a dimeric enzyme that catalyses the interconversion of carbon dioxide and carbonic acid. The precursor form of Cr-alphaCA1 undergoes post-translational cleavage and N-glycosylation. Comparison of the genomic sequences of precursor Cr-alphaCA1 and other alphaCAs shows that Cr-alphaCA1 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-alphaCA1 has been determined at 1.88 A 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 beta-sheet structure composed of nine beta-strands. At the centre of the beta-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 alphaCAs. 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-alphaCA1 activity.