Overexpression and purification of Helicobacter pylori flavodoxin and induction of a specific antiserum in rabbits

Flavodoxin from the gastric pathogen Helicobacter pylori has been shown to be the electron acceptor of the essential pyruvate-oxidoreductase enzyme co mplex and proposed to be involved in the pathogenesis of gastric MALToma. I n order to obtain a sufficient amount for biochemical and structural studie s, we overexpressed the protein either with a C-terminal His(6)-tag or as a fusion protein upstream of intein- and chitin-binding domains. With both e xpression systems we succeeded at purifying soluble and functional flavodox in containing the cofactor FAIN. When expressing with a His(6)-tag, we puri fied similar to 20 mg flavodoxin per liter of bacterial culture, while expr ession as an intein-CBD fusion protein with autocatalytic removal of the in tein-CBD part rendered only similar to1 mg of purified flavodoxin per liter of bacterial culture. Expressed as an intein-CBD fusion protein, flavodoxi n copurified with a C-terminal degradation product, which was not observed for expression with a His(6)-tag. However, we were able to obtain protein c rystals suited for X-ray structure determination from flavodoxin expressed as an intein-CBD fusion protein, but not from flavodoxin expressed with a C -terminal His(6)-tag. We further report the induction of a rabbit antiserum specific for H. pylori flavodoxin. (C) 2001 Academic Press.