The role of His 16, Tyr 82 and Trp 86 in color shift, activity and thermostability of aequorin photoprotein

Aequorin is a calcium sensitive photoprotein composed of apoaequorin (189 amino acid), oxygen and coelenterazine (imidazopyrazine chromophore). Activity of this photoprotein in calcium presence is blue photon emission (469 nm). Studies have shown that three amino acids H16, Y82, W86 are involved in color shift and activity of Aequorin. In this work, for study of structural-functional relationship, combinational mutant was used for determine of the interest places importance in single and combination state. Using site directed mutagenesis, the single and multiple mutations done in plasmid and mutated aequorin in single and multiple states were prepared. Next, thermostability, activity and color shift of produced protein determined using luminometer and spectrofluorimetry, respectively. We found that W86 and H16 play a more critical role in color shift and activity respectively. In addition, mutation of W86 provides better termostability compared to other mutations. This investigation was shown that the role of W86 in aequorin shift light and thermostability is better than Y82 and H16 and this mutant could be used for effective protein production in sensor and other applications.