The vitamin A derivative 11-cis-retinaldehyde plays a pivotal role in vertebrate vision by serving as the chromophore of rod and cone visual pigments. In the initial step of vision, a photon is absorbed by this chromophore resulting in its isomerization to an all-trans state and consequent activation of the visual pigment and phototransduction cascade. Spent chromophore is released from the pigments through hydrolysis. Subsequent photon detection requires the delivery of regenerated 11-cis-retinaldehyde to the visual pigment. This trans–cis conversion is achieved through a process known as the visual cycle. In this review, we will discuss the enzymes, binding proteins and transporters that enable the visual pigment renewal process with a focus on advances made during the past decade in our understanding of their structural biology.
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Cover Image
Cover Image
In this issue of the Biochemical Journal, Müller et al. report on the role of inorganic polyphosphate (polyP) and ATP during the initial state of microvascularization. The research shows that exposure of endothelial cells to energy-rich polyP accelerates an autocrine mechanism involved in cell migration via induction of ATP production both extracellularly and intracellularly. For details, see pages 3255–3273. The cover image shows the journey of polyP from its release by platelets to the formation of extracellular ATP and the induction of intracellular ATP production via glycolysis close to the cell membrane, resulting in the generation of an ATP gradient that enables chemotaxis to occur. The image was kindly provided by Werner E.G. Müller and Xiaohong Wang.
Structural biology of 11-cis-retinaldehyde production in the classical visual cycle
