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The acid-induced arginine decarboxylase is part of an enzymatic system in Escherichia coli that contributes to making this organism acid resistant. The arginine decarboxylase is a vitamin B(6)-dependent enzyme that is active at acidic pH. It consumes a proton in the decarboxylation of arginine to agmatine, and by working in tandem with an arginine-agmatine antiporter, this enzymatic cycle protects the organism by preventing the accumulation of protons inside the cell. We have determined the structure of the acid-induced arginine decarboxylase by X-ray crystallography to 2.4 A resolution. The arginine decarboxylase structure revealed a ca. 800 kDa decamer composed as a pentamer of five homodimers. Each homodimer has an abundance of acidic surface residues, which at neutral pH prevents inactive homodimers from associating into active decamers. Conversely, acidic conditions favor the assembly of active decamers. Therefore, the structure of arginine decarboxylase presents a mechanism by which its activity is modulated by external pH.

Original publication

DOI

10.1021/bi900075d

Type

Journal article

Journal

Biochemistry

Publication Date

12/05/2009

Volume

48

Pages

3915 - 3927

Keywords

Acids, Biopolymers, Carboxy-Lyases, Crystallography, X-Ray, Enzyme Induction, Escherichia coli, Hydrogen-Ion Concentration, Models, Molecular, Protein Conformation