Bioinformatics investigation of the structure and function of mnemiopsin2 following proline 181 substitutions using a site-directed mutagenesis

Mnemiopsin2 belongs to the family of calcium-regulated photoproteins, which like other photoproteins, begins to emit light in the presence of substrates such as coelenterazine, molecular oxygen, and calcium initiator ion. Proline 181 in mnemiopsin is the eleventh residue of the EF-hand IV loop. Since EF-hand IV is one of theactive loops in binding to calcium, we replaced the proline 181 with residues of alanine (neutral, in order to reduce the space interference of this position), lysine (a positive charge residue, in order to strengthen the dipolar moment at C terminus), and aspartic acid (a negative charge residue in order to follow the first structure of aequorin photoprotein in the same position). Thereafter, the effect of these changes was evaluated on mnemiopsin2 function. For this, the mutation models were designed using the Moderller9v19 software. Then, the best wild and mutated models were selected and evaluated using ModEval, SAVES, SPdbViewer software and PIC Server. In the following, the status of interactions and biochemicalphysical properties of wild and mutated proteins were investigated. The 3D structure was also designed by Chimera software. The results of the interactions analysis by the PIC server have been shown to that the hydrophobic interactions between the main chain and the mutated P181D have decreased, and in two other mutations, the increase in the wild type. The study of ionic interactions has shown that the mutation in P181A decreased and the two mutants showed an increase. Also, the index of Instability Index derived from the Prot Param server has shown that to enhance the structural stability all of the three has been mutations.

Keywords:

Photoprotein , Mnemiopsin2 , Site-directed mutagenesis , Proline 181 residue , Stability