N-15 LABELING METHOD OF PEPTIDES USING A THIOREDOXIN GENE FUSION EXPRESSION SYSTEM - AN APPLICATION TO ACTH-(1-24)

For structure analysis of peptides by multinuclear MMR, stable isotope -labeled samples are required. A direct overexpression system by E. co li cells does not work for that purpose because of rapid degradation o f the peptides and/or the mRNA in host cells. We here developed an ove r-expression system by means of thioredoxin gene fusion system. The fu sed protein composed of thioredoxin and the objective peptide was expr essed in E. coli and then the peptide part was released by enterokinas e. This system was successfully applied for the production of N-15- la beled human adrenocorticotropic hormone fragment (ACTH-(1-24)) as need ed for multinuclear MMR analysis.