Cell-free protein synthesis for structure determination by X-ray crystallography.

Miki Watanabe, Ken ichi Miyazono, Masaru Tanokura, Tatsuya Sawasaki, Yaeta Endo, Ichizo Kobayashi

Research output: Contribution to journalArticlepeer-review

22 Citations (Scopus)


Structure determination has been difficult for those proteins that are toxic to the cells and cannot be prepared in a large amount in vivo. These proteins, even when biologically very interesting, tend to be left uncharacterized in the structural genomics projects. Their cell-free synthesis can bypass the toxicity problem. Among the various cell-free systems, the wheat-germ-based system is of special interest due to the following points: (1) Because the gene is placed under a plant translational signal, its toxic expression in a bacterial host is reduced. (2) It has only little codon preference and, especially, little discrimination between methionine and selenomethionine (SeMet), which allows easy preparation of selenomethionylated proteins for crystal structure determination by SAD and MAD methods. (3) Translation is uncoupled from transcription, so that the toxicity of the translation product on DNA and its transcription, if any, can be bypassed. We have shown that the wheat-germ-based cell-free protein synthesis is useful for X-ray crystallography of one of the 4-bp cutter restriction enzymes, which are expected to be very toxic to all forms of cells retaining the genome. Our report on its structure represents the first report of structure determination by X-ray crystallography using protein overexpressed with the wheat-germ-based cell-free protein expression system. This will be a method of choice for cytotoxic proteins when its cost is not a problem. Its use will become popular when the crystal structure determination technology has evolved to require only a tiny amount of protein.

Original languageEnglish
Pages (from-to)149-160
Number of pages12
JournalMethods in molecular biology (Clifton, N.J.)
Publication statusPublished - 2010 Jan 1
Externally publishedYes

ASJC Scopus subject areas

  • Molecular Biology
  • Genetics


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