Interaction in vitro; enzyme produced as a recombinant fusion protein in bacterial system.

In the absence of His3 peptide, trx SET domain automethylates itself at the Cys3641 residue.

The trx SET domain was incubated in the presence of [3]H-methyl-S-adenosylmethionine, with or without the His3 N-terminal peptide. Samples were then separated by SDS-PAGE and methylation of the trx band was assessed by autoradiography.