Open AccessThere is a baby in the bath water: AcrB contamination is a major problem in membrane‐protein crystallization
Author(s) -
Veesler David,
Blangy Stéphanie,
Cambillau Christian,
Sciara Giuliano
Publication year - 2008
Publication title -
acta crystallographica section f
Language(s) - English
Resource type - Journals
ISSN - 1744-3091
DOI - 10.1107/s1744309108028248
Subject(s) - crystallization , escherichia coli , contamination , acriflavine , chemistry , membrane protein , molecular replacement , resolution (logic) , membrane , affinity chromatography , crystallography , chromatography , biochemistry , biology , organic chemistry , ecology , artificial intelligence , computer science , gene , enzyme
In the course of a crystallographic study of the Methanosarcina mazei CorA transporter, the membrane protein was obtained with at least 95% purity and was submitted to crystallization trials. Small crystals (<100 µm) were grown that diffracted to 3.42 Å resolution and belonged to space group R 32, with unit‐cell parameters a = b = 145.74, c = 514.0 Å. After molecular‐replacement attempts using available CorA structures as search models failed to yield a solution, it was discovered that the crystals consisted of an Escherichia coli contaminating protein, acriflavine resistance protein B (AcrB), that was present at less than 5% in the protein preparations. AcrB contamination is a major problem when expressing membrane proteins in E. coli since it binds naturally to immobilized metal‐ion affinity chromatography (IMAC) resins. Here, the structure is compared with previously deposited AcrB structures and strategies are proposed to avoid this contamination.