A simple, rapid method for the production of soluble recombinant proteins from the duplicated growth hormone genes of the tetraploid common carp

The simple protein production method developed in the present study enables the production of large quantities of active recombinant common-carp growth hormone proteins in a few brief steps. With this method, the recombinant protein is obtained in a soluble form without the need for refolding. This method can be utilised for determining if the two common-carp growth hormones have similar functions in vitro and in vivo and what role each plays in growth regulation. If differences in activity exist, this method can also be used to produce intermediate forms of the two common carp growth hormones rapidly in order to determine which of the six amino acids that differ between the two proteins are responsible for the altered activity. Common carp has the same tetraploid ancestor as goldfish, and the products of the growth hormone paralogues in goldfish also differ. It would be interesting to understand how the same duplicated orthologues have evolved, and the methods elaborated in this study could be used for such comparative investigations