Our vision can adapt to change between bright light and dark, but it takes a moment because the in our receptor cells must break apart into and for light adaptation and recombine for dark adaptation.

Our vision can adapt to change between bright light and dark, but it takes a moment because the rhodopsin in our receptor cells must break apart into all-trans-retinal and scotopsin for light adaptation and recombine for dark adaptation.  

Rhodopsin is a pigment-containing sensory protein (photopigment) that converts light into an electrical signal. Rhodopsin consists of 11-cis retinal combined with scotopsin. When rhodopsin absorbs light, retinal changes from 11-cis to all-trans retinal and the retinal-scotopsin complex breaks down. This process is called bleaching of the pigment and it triggers a signal transduction along the optic nerve to the visual cortex in the brain.
In the dark, rhodopsin regenerates.

Pro insulin undergoes extensive posttranslational modification along the production pathway .