Crystal structure of the acid-induced arginine decarboxylase from Escherichia coli: Reversible decamer assembly controls enzyme activity

Abstract

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 B6-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 Å resolution. The arginine decarboxylase structure revealed a ca. 800 kDa decamer composed as a pentamer of five homodime..