Human recombinant tyrosinase destabilization caused by the double mutation R217Q/R402Q

Oculocutaneous albinism is an autosomal recessive inherited disorder associated with mutations in the TYR gene. A single missense change in the tyrosinase (Tyr) could result in partial or complete loss of catalytic activity. The effect of two genetic mutations in the same Tyr as the molecule is less studied. Here, we study single mutation variants, R217Q, R402Q, and a double mutant variant, R217Q/R402Q, to establish a link between alterations at the level of the atomic model of the protein and the disease phenotype. Human recombinant intra-melanosomal Tyr domains of Tyr and three mutant variants were expressed in T. ni. Larvae were purified using the combination of IMAC and SEC, and diphenolase activities were measured. The Tyr homology model was equilibrated using 100 ns molecular dynamics and analyzed using computational methods. The purified R217Q and R217Q/R402Q variants show decreased catalytic activities compared to those of the Tyr and R402Q variants. The R217Q/R402Q variant has the lowest protein activity and is significantly reduced.