Scientists led by the Institut de Biologie Structurale have combined advanced X-ray methods to unveil how a photoreceptor regulates carotenoid production in bacteria, including experiments at the ESRF. The results are out in Nature.
CarH is a photoreceptor which senses light through a vitamin B12 derivative and regulates carotenoid expression through direct interaction with genes. Bacteria use this remarkable machinery to regulate gene expression and produce carotenoid to protect themselves from photo-damage upon sun exposure. What scientists had never seen before was how tiny photoinduced changes at the vitamin B12 level, propagate into large-scale structural changes triggering a biological response. Now, an international collaboration has managed to film this process in unprecedented detail, with key experiments carried out at the ESRF and at XFELs.
CarH’s role has been clear since around 2015. In the dark, the protein binds to DNA and blocks the production of carotenoids. When light is present, CarH releases the DNA, allowing the cell to produce carotenoids that help defend against light-induced damage.
Previous crystal structures revealed the start and end points of this process. But the crucial missing piece was the journey in between — from the short-lived structural changes that occur immediately after light hits the vitamin B12 molecule to the large-scale conformational changes involving the whole protein structure and its interaction with DNA.
Read more on the ESRF website
Image credit: CEA and Maria Davila Miliani
