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Biotechnology and Applied Biochemistry (2000) 31, (91–94) (Printed in Great Britain)

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High-level expression of tetanus toxin fragment C–thioredoxin fusion protein in Escherichia coli

Adriana V. Ribas, Paulo L. Ho, Martha M. Tanizaki, Isaias Raw and Ana L. T. O. Nascimento¹

Center of Biotechnology, Instituto Butantan, Av. Vital Brasil, 1500, CEP 05503–900, São Paulo, SP, Brazil

¹ To whom correspondence should be addressed.

An insert of Clostridium tetani DNA corresponding to fragment C of tetanus toxin was amplified by PCR. This 1.4 kb fragment was cloned into the high-expression vector pET32a, under control of the T7 promoter. Expression of this plasmid in Escherichia coli BL21(DE3) resulted in the production of a fusion protein ( 62 kDa) consisting of 112 amino acids of thioredoxin and 450 amino acids of fragment C. This fusion protein was recognized by anti-tetanus toxoid antiserum in an ELISA and on immunoblots. The recombinant fragment-C-thioredoxin protein was purified significantly in one step by Ni²⁺-chelate Sepharose, the final yield being 35 mg/l. Immunization of animals with the recombinant protein produced antibodies that were able to recognize the tetanus toxin. By using this gene-fusion expression system we produced soluble fragment C of tetanus toxin in a high yield, preventing many problems inherent in the use of other expression systems that produce either insoluble fragment C in inclusion bodies, or a soluble form, but in low yield, using E. coli as the expression host.

Received 2 September 1999/17 November 1999; accepted 19 November 1999

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