Rhodopsin, Zn(2+), and retinitis pigmentosa: a short tale requiring continuation

Understanding the relationship between the visual pigment rhodopsin and Zn2+ under normal conditions and in case of deficiency of the latter, as well as the realization of the role of Zn2+ in the development of the hereditary disease retinitis pigmentosa, have great theoretical and practical importance. In this mini-review, we briefly examine the basic experimental data on the role of Zn2+ in the retina and photoreceptors, binding of endogenous Zn2+ by zinc-binding sites of differing affinities in rhodopsin, the influence of the exogenous Zn2+ on various properties of rhodopsin, including its ability for phosphorylation and activation of transducin, as well as its thermal stability and regeneration. Conflicting results on the correlation between Zn2+ content in the blood serum and the development of retinitis pigmentosa in patients are demonstrated. The review also shows the success of the application of animal models of induced or hereditary retinal degeneration and discusses some of the methodological approaches and therapeutic techniques to relieve the manifestations of this disease.