Sensory SystemsSensory SystemsСенсорные системы0235-00923034-5936The Russian Academy of Sciences69674910.7868/S3034593625030019ОБЗОРЫResearch ArticleFree and bound fraction of cGMP in the outer segment of vertebrate photoreceptorsСвободная и связанная фракция cGMP в наружном сегменте фоторецепторов позвоночныхFirsovM. L.ФирсовМ. Л.Michael.Firsov@gmail.comSechenov Institute of Evolutionary Physiology and Biochemistry RASИнститут эволюционной физиологии и биохимии им. И.М. Сеченова РАН15122025393VOL 39, NO3 (2025)ТОМ 39, №3 (2025)31221112025Copyright ©; 2025, Russian Academy of SciencesCopyright ©; 2025, Российская академия наук2025Russian Academy of SciencesРоссийская академия наукhttps://journals.eco-vector.com/0235-0092/article/view/696749

The phototransduction cascade in vertebrate retinal photoreceptors uses cyclic guanosine monophosphate (cGMP) as a secondary messenger. The level of cGMP controls the conductance of channels in the plasma membrane of the cell, so the rate at which the level of cGMP changes is critical for photoreceptor responsiveness. There is an apparent contradiction between the high total concentration of cGMP in the outer segments and the high rate of cGMP exchange measured experimentally. The contradiction can be resolved by assuming that most of the cGMP is in the bound state and that the dynamic fraction is a small fraction of the total cGMP, but it is this fraction that is altered by light and controls channel conductance. In this review, we discuss the evidence for the partitioning of the total cGMP pool into bound and free fractions, the likely cGMP binding sites, and the possible functional significance of the existence of the two fractions.

Каскад фототрансдукции в фоторецепторах сетчатки позвоночных использует в качестве вторичного мессенджера циклический гуанозинмонофосфат (cGMP). Уровень cGMP управляет проводимостью каналов плазматической мембраны клетки, поэтому скорость, с которой меняется уровень cGMP, является критической для быстродействия фоторецептора. Существует кажущееся противоречие между высокой общей концентрацией cGMP в наружных сегментах и экспериментально измеренной высокой скоростью обмена cGMP. Противоречие может быть разрешено, если предположить, что большая часть cGMP находится в связанном состоянии, а динамическая фракция составляет незначительную долю от общего cGMP, но именно она изменяется под действием света и управляет проводимостью каналов. В настоящем обзоре мы разбираем доказательства разделения общего пула cGMP на связанную и свободную фракцию, вероятные сайты связывания cGMP и возможное функциональное значение существования двух фракций.

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