Intra-electron transfer of amicyanin from newly derived active site to redox potential tuned type 1 copper site
Amicyanin, one of the type I copper proteins which has been used for the study, mediates the electron transfer reaction between methylamine dehydrogenase and cytochrome c-551i in Paracoccus denitrificans for energy production. The 6×Histidine-tag site which has been widely used in purification of a recombinant protein was introduced at the N-terminus of amicyanin to make the complex of 6×His-tagged plus cobalt functioning as a newly derived redox cofactor in amicyanin. In this study, Pro94 of amicyanin was substituted to Ala and Phe to tune up the midpoint potential (Em) value of amicyanin 100 mV more positive and then intra-electron transfer rates were measured to examine whether the Em value of the type 1 copper site in amicyanin affects intraprotein electron transfer or not. By the addition of H2O2, the Co2+-loaded 6×His-tagged site was activated, and then electron was transferred from Cu1+ of type 1 copper site of amicyanin to Co3+ plus 6×His-tagged site. Electron transfer rates of cobalt loaded P94A and F amicyanin were much slower than that of native amicyanin. These results suggest that the communication between the newly protein-derived redox cofactor, 6×His-tagged site plus cobalt, and type 1 copper site is truly occurred and that the strength of electron transfer reaction between them is able to be controlled by an Em value.
KeywordsAmicyanin Cofactor Protein engineering Redox potential 6×His-tag
This work is supported by NRF Grants (2016R1C1B1008673 and 2016R1C1B2008836).
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