Ca²⁺ Binding and Conformational Switch of the Photoprotein Mnemiopsin

Title:Ca²⁺ Binding and Conformational Switch of the Photoprotein Mnemiopsin

Volume: 24 Issue: 6

Author(s): Shima Tarahomi, Reza H. Sajedi*, Hossein Rahmani, Bijan Ranjbar and Majid Taghdir

Affiliation:

• Department of Biochemistry, Faculty of Biological Sciences, Tarbiat modares University, Tehran,Iran

Keywords: EF-hand calcium-binding proteins, photoproteins, mnemiopsin, conformational switch, flexibility, proteolysis.

Abstract: Background: Bioluminescence in Ca²⁺-binding photoproteins is an intramolecular reaction triggered by the addition of Ca²⁺. A comparative study has been done on Ca²⁺-depleted and Ca²⁺-loaded apo-mnemiopsin to understand the structural transition of the photoprotein by Ca²⁺ binding. Ca²⁺ is removed by TCA (trichloroacetic acid) precipitation to obtain Ca²⁺-depleted apomnemiopsin.

Method: UV–visible, CD and fluorescence spectroscopic studies demonstrate that the addition of Ca²⁺ is brought about by the overall structure of apo-mnemiopsin becomes more open in a concentration- dependent manner without significantly influencing the secondary structure and indicate that the Ca²⁺-depleted form of apo-mnemiopsin, in contrast to most other EF-hand calcium binding proteins, adopt a closed conformation when compared to the Ca²⁺-loaded form. On the other hand, dynamic quenching and limited proteolysis analysis revealed that Ca²⁺-loaded apo-mnemiopsin became much more flexible than Ca²⁺ free apo-mnemiopsin.

Results: It seems that increased flexibility of the protein, which occurs due to calcium binding, is a critical factor in oxidative decarboxylation reaction on coelenterazine and consequently light emission.

Cite this article as:

Tarahomi Shima , Sajedi H. Reza*, Rahmani Hossein , Ranjbar Bijan and Taghdir Majid , Ca²⁺ Binding and Conformational Switch of the Photoprotein Mnemiopsin, Protein & Peptide Letters 2017; 24 (6) . https://dx.doi.org/10.2174/0929866524666170310110318

DOI https://dx.doi.org/10.2174/0929866524666170310110318	Print ISSN 0929-8665
Publisher Name Bentham Science Publisher	Online ISSN 1875-5305