Image_2_Characterization of a Dimeric Arginase From Zymomonas mobilis ZM4.TIF (414.3 kB)
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Image_2_Characterization of a Dimeric Arginase From Zymomonas mobilis ZM4.TIF

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posted on 2019-11-26, 04:25 authored by Seung-A Hwangbo, Ji-Won Kim, Sun-Ju Jung, Kyeong Sik Jin, Jie-Oh Lee, Jeong-Sun Kim, Suk-Youl Park

Many organisms have genes to protect themselves from toxic conditions such as high ethanol and/or ammonia concentrations. When a high ethanol condition is induced to Zymomonas mobilis ZM4, a representative ethanologenic organism, this bacterium overexpresses several genes to overcome this ethanol stress. Among them, we characterized a gene product annotated as an arginase (zmARG) from Z. mobilis ZM4. Even though all of the arginase-determining sequence motifs are not strictly conserved in zmARG, this enzyme converts L-arginine to urea and L-ornithine in the presence of a divalent manganese ion. The revealed high-resolution crystal structure of zmARG shows that it has a typical globular α/β arginase fold with a protruded C-terminal helix. Two zinc ions reside in the active site, where one metal ion is penta-coordinated and the other has six ligands, discerning this zmARG from the reported arginases with two hexa-liganded metal ions. zmARG forms a dimeric structure in solution as well as in the crystalline state. The dimeric assembly of zmARG is formed mainly by interaction formed between the C-terminal α-helix of one molecule and the α/β hydrolase fold of another molecule. The presented findings demonstrate the first reported dimeric arginase formed by the C-terminal tail and has two metal ions coordinated by different number of ligands.