Humboldt-Universität zu Berlin - Experimentelle Biophysik

Rhodopsins are photoresponsive proteins that play a crucial role in visual orientation of various organisms such as animals, algae, fungi and bacteria. Light-absorption in rhodopsins occurs by harboring the photosensitive chromophore retinal. Furthermore, a rhodopsin can be bound to an enzyme, forming a light-regulated catalytic unit (enzymerhodopsin). Recently, first rhodopsin-guanylyl cyclases were found in unicellular aquatic fungi of the division Blastocladiomycota [1]. During light-activation, these enzymerhodopsins produce the second messenger cGMP by cleaving GTP.

The aim of my PhD is the functional characterization of rhodopsin-guanylyl cyclases, in particular from the fungus Rhizoclosmatium globosum [2]. Therefore, we are expressing recombinant proteins in various expression systems (E. coli, yeast, Xenopus oocytes) and using biochemical and biophysical methods (e.g. reversed-phase HPLC, ELISA, electrophysiology) to obtain structural insights.

[1] Scheib U., Stehfest K., Gee C., Körschen H., Fudim R., Oertner T., Hegemann P. (2015) “The rhodopsin-guanylyl cyclase of the aquatic fungus Blastocladiella emersonii enables fast optical control of cGMP signaling” Science Signaling, 8(389)

[2] Broser M., Sierra Y., Konold P., Peter E., Adam S., Borin V., Schapiro I., Seifert R., Kennis J., Hegemann P. (2020) “Light sensing beyond red: NeoR, a near-infrared absorbing rhodopsin” Nature Communications, 11(5682)