Cloning and expression of rapeseed procruciferin in Escherichia coli and crystallization of the purified recombinant protein.

Two rapeseed cruciferin cDNAs (cru2/3a and cru2/3b) were cloned and sequenced. A comparison of their DNA and protein sequences with other cruciferins, indicated cru2/3b to be a novel clone and, among them, an inherent and highly conserved sequence of twelve amino acids was identified. Procruciferin 2/3a and 2/3b were expressed in Eschericha coli, and procruciferin 2/3a was obtained in a soluble form. The expressed procruciferin 2/3a has a trimeric structure and formed crystals although the quality was not good, suggesting that this expression system is useful for protein engineering of procruciferin 2/3a.