PMID: 14660577

 

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Title : Expression, assay, and structure of the extracellular domain of murine carbonic anhydrase XIV : implications for selective inhibition of membrane-associated isozymes

Abstract :

1. Carbonic anhydrase (CA) XIV is the most recently identified mammalian carbonic anhydrase isozyme, and its presence has been demonstrated in a number of tissues
2. Full-length CA XIV is a transmembrane protein composed of an extracellular catalytic domain , a single transmembrane helix, and a short intracellular polypeptide segment
3. The amino acid sequence identity of human CA XIV relative to the other membrane-associated isozymes ( CA IV , CA IX , and CA XII ) is 34-46%
4. We report here the expression and purification of both the full-length enzyme and a truncated, secretory form of murine CA XIV
5. Both forms of this isozyme are highly active, and both show an abrogation of activity in the presence of 0.2% SDS , in contrast to the behavior of murine CA IV
6. We also report the crystal structure of the extracellular domain of murine CA XIV at 2.8 A resolution and of an enzyme-acetazolamide complex at 2.9 A resolution
7. The structure shows a monomeric glycoprotein with a topology similar to that of other mammalian CA isozymes
8. Based on the x-ray crystallographic results, we compare and contrast known structures of membrane-associated CA isozymes to rationalize the structural elements responsible for the SDS resistance of CA IV and to discuss prospects for the design of selective inhibitors of membrane-associated CA isozymes