Biochemistry I   Spring & Fall Terms

Carbonic Anhydrase

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Carbonic Anhydrase Structure
Carbonic Anhydrase (2cba.pdb) catalyzes the reversible hydration of CO2 to form bicarbonate anion and a proton:
CO2 + H2O <==> HCO3- + H+
The overall architecture is described as a 10-stranded (mostly) antiparallel b-sheet; the b-sheet is surrounded by various elements of other secondary structure. The bicarbonate product (labeleled "BCT") is shown at the active site. The amino and carboxyl termini of the protein are labeled.
The starting Display is Cartoons; the Color is Structure.
The active site Zn2+ is Spacefill colored CPK. It is located near the center of the protein at the bottom of a 15 Å funnel-shaped cleft. The zinc is coordinated by three histidine side chains and a OH- ion when it reacts with CO2. (Hit the "Spacefill & Zoom" button for a closer look.)

Two Toggle buttons show details at the active site:
1. The first alternately shows CO2 + OH- or HCO3- at the catalytic Zn atom.
2. The second alternately shows an inhibitor (acetazolamide, and labeled "AZM") at the active site. Note the steric overlap between AZM and either reaction substrate.
[Figure not in Campbell]

A more detailed look at the carbonic anhydrase active site and the steps involved in its catalytic action are shown on the Carbonic Anhydrase Mechanism page.

Back to the Protein Structure List.

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10.4.04