Volume 18, Number 2, pp. 94–98
Modeling the allosteric effect in visual rhodopsin due to phosphorylation
Nona Vasilieva-Vashakmadze,1 Giorgi Lekishvili,2 Polina Toidze1 and Ramaz Gakhokidze1
1 Javakhishvili State University, 3 Chavchavadze Ave, 0179 Tbilisi, Georgia
2 Tbilisi State Medical University, 33 Pshavela Ave, 0186 Tbilisi, Georgia
The possible mechanism of experimentally observed conformational changes in visual rhodopsin is considered; i.e., the allosteric effect occurring late in the photocycle during phosphorylation of the tail fragment of opsin. The methods of physics and quantum chemistry (microscopic and macroscopic approaches) allowed us to obtain relations showing the inner relationship between the shift of electron density under the influence of substituents or ligands (i.e., mesomeric and inductive effects) on the one hand and, on the other, a conformational shift (allosteric effect) in the a-helical protein subunits following phosphorylation of the a-helix VII subunit fragment of visual rhodopsin. It is shown that, resulting from phosphorylation of serine residues at the C-terminal fragment, opsin changes its electron density distribution, extending along the chain of atoms; i.e., mesomeric and inductive effects cause a conformational shift (an allosteric effect in the a-helical subunits of opsin).
Keywords: allosteric effect, conformational changes, mesomeric effect, visual rhodopsin
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