An in silico analysis on the photoproteins Mnemiopsin 1 and Mnemiopsin 2 to explain the experimental results

Abstract

Mnemiopsin 1 (Mn1) and Mnemiopsin 2 (Mn2) are photoproteins found in Mnemiopsis leidyi. We have tried to answer the question of whether the structural features of photoproteins can explain the observed activity data. According to the activity measurements data, they have the same characteristic wavelength. However, initial intensity of Mn2 is significantly higher than that of Mn1, and decay time of Mn1 (0.92 s‐1) is lower than that of Mn2 (1.46 s‐1). The phylogenetic analysis demonstrates that compared with Obelin and Aequorin from Obelia longissima and Aequorea victoria, respectively, a gene modification event may have caused the expansion of the N‐terminal side of all photoproteins from Mnemiopsis leidyi. In silico study has shown that the stability of the photoprotein‐substrate complex of Mn2 is higher than that of Mn1, indicating higher affinity of the substrate for Mn2 compared with Mn1. It was revealed that the active EF‐hand loop 1 and III in Mn2 is locally more rigid compared with those in Mn1. We concluded that different stability of the photoprotein complexes leads to different initial intensity. While different pattern of the local dynamics of loops I and III may influence the decay rate.