Abstract: To determine the structure of BetA fromPseudomonas denitrificans, the recombinant plasmid pET-28a-PdBetA was constructed to express and purifyPdBetA protein for crystallization experiments. X-ray diffraction analysis of the protein crystals yielded a 1.8  resolution structure ofPdBetA. ThePdBetA structure consists of a β sandwich fold comprising an antiparallel three-stranded β-sheet together with a parallel five-stranded β-sheet, and an antiparallel six-stranded β-sheet with two approximately parallel α-helices on the same side. Structural comparison and sequence alignment with its homologs suggested a potential flavin adenine dinucleotide binding pocket inPdBetA.

Key words: vitamin B₁₂;Pseudomonas denitrifican, betaine, choline dehydrogenase（BetA）, crystal structure