"Sunlight is the basis for all life on Earth so it should come as no surprise that many organisms have developed complex systems for detecting the quality and quantity of light in their environment. Plants, fungi, and many species of bacteria use light-sensitive proteins called phytochromes to control biological functions that respond to changes in light. In the bacterial species Deinococcus radiodurans, a red/far-red-light absorbing phytochrome controls the production of light-protective pigments.
For this, they crystallized the phytochrome in both
In the resting state, the tongue forms a β-sheet secondary protein structure. Absorption of red
light by the Pr form causes dramatic changes in the protein. The two halves of the dimer adopt an "open" conformation, widening the gap between them by several nanometers. Remarkably, the tongue now converts to a completely different protein secondary structure and adopts a much shorter, α-helical conformation. The new tongue is 2.5 angstroms shorter and interacts with different conserved amino acids than the resting state tongue. This change is sufficient to explain how the active state of the protein may transmit changes to the next protein in the signaling cascade in response to light.
The data obtained by the team provide the sequences of steps required to convert light into action. First, red light absorption causes changes in the chromophore at the atomic level, which are amplified and transmitted to the surrounding phytochrome. These changes result in dramatic rearrangement of the tongue, which shortens by 2.5 angstroms. Shortening of the tongue causes a shift in the rigid dimer structure of the phytochrome and the dimer "opens" by several nanometers. The conformational signal is amplified from a small nudge at the atomic level to a dramatic protein rearrangement on the nanometer scale. Action!" Phys.org
For this, they crystallized the phytochrome in both
the resting, Pr (red-absorbing)
and active, Pfr (far-red absorbing) state.
Both structures showed that the phytochrome forms a dimer with two copies of the protein forming a single unit. In the resting state, the dimer is in a "closed" configuration and a highly evolutionarily conserved amino acid sequence forms a tongue-like structure (see the figure).In the resting state, the tongue forms a β-sheet secondary protein structure. Absorption of red
The data obtained by the team provide the sequences of steps required to convert light into action. First, red light absorption causes changes in the chromophore at the atomic level, which are amplified and transmitted to the surrounding phytochrome. These changes result in dramatic rearrangement of the tongue, which shortens by 2.5 angstroms. Shortening of the tongue causes a shift in the rigid dimer structure of the phytochrome and the dimer "opens" by several nanometers. The conformational signal is amplified from a small nudge at the atomic level to a dramatic protein rearrangement on the nanometer scale. Action!" Phys.org
And God said, Let there be light: and there was light.
Genesis 1:3