Prof. Dr. Volodymyr Korkhov

Interactions between the cell and its environment, as well as between different cellular compartments, occur at the biological membranes. Extracellular signals are sensed by the receptors at the cell surface. These signals are then transmited across the membrane via multiple biomolecular interactions involving membrane-bound and soluble proteins, resulting in complex biochemical responses inside the cell. The process of signal transduction is critically important for physiology in health and disease. The research in my group is focused on understanding the molecular mechanisms of signal transduction. Using a multidisciplinary approach including methods of membrane protein biochemistry, biophysics and structural biology (including X-ray crystallography and cryo-EM), we aim to understand the structure-function relationships of membrane proteins and protein complexes involved in various aspects of cellular signalling. We are particularly interested in membrane protein complexes in two areas of signalling: (i) the cyclic adenosine monophosphate (cAMP) pathway, (ii) the Hedgehog signalling pathway.
 

1. Cryo-EM structure of membrane adenylyl cyclase-G protein complex

The structure of adenylyl cyclase-9 (AC9) bound to an activated G protein as subunit, solved at a resolution of 3.4 Å by cryo-EM and single particle analysis, reveals the organization of a complete AC-Ga protein complex. The structure features the key domains of the membrane AC: the membrane domain, the cytosolic catalytic domain, and the helical domain that connects the membrane and the catalytic portions of AC9. The structure also features a C-terminal peptide occluding the catalytic and allosteric sites of AC9. The occluded state of the AC is distinct from its substrate- and activator-bound state. The structural and biochemical evidence provides new insights into the auto-regulatory function of the C-terminus. The natural ligand for the AC allosteric site has until now remained unknown, and thus the results hint at the potential physiological role of the allosteric site of the membrane ACs in direct protein-protein interactions. Similar modes of regulation may apply to other membrane ACs.

Qi et al., Science, 2019

https://science.sciencemag.org/content/364/6438/389

2. Cryo-EM structure of the human PTCH1 bound to a modified Sonic Hedgehog ligand

The Hedgehog signalling pathway has an important role in tissue patterning during embryonic development and is linked to human disease. Binding of Sonic Hedgehog morphogen, Shh, to PTCH1 initiates the Hedgehog signalling cascade. PTCH1 has been suggested to act as a transporter for cholesterol, and this transport activity apparently underlies its role in controlling the Hedgehog pathway. We have determined the 3.4 Å resolution structure of PTCH1 bound to a Hedgehog ligand variant ShhN_C24II using cryo-EM and single particle analysis. A set of sterol molecules was observed bound in positions within the outer and inner leaflet of the membrane at the Sterol Sensing Domain (SSD) and the SSD-like domain of PTCH1. The structure suggests a possible route for sterol translocation across the lipid bilayer mediated by PTCH1 and related transporters.

Qi et al., Sci Adv, 2019

https://advances.sciencemag.org/content/5/9/eaaw6490

1. Vercellino I. Rezabkova L., Olieric V., Polyhach Y., Weinert T., Kammerer R.A., Jeschke G., Korkhov V.M. Role of the nucleotidyl cyclase helical domain in catalytically active dimer formation. Proc Natl Acad Sci U S A. (2017) 114, E9821-E9828.

2. Qi C., Sorrentino S., Medalia O., Korkhov V.M. The structure of a membrane adenylyl cyclase bound to an activated stimulatory G protein. Science (2019) 364, 389-394.

3. Qi C., Di Minin G., Vercellino I., Wutz A., Korkhov V.M. Structural basis of sterol recognition by human hedgehog receptor PTCH1. Sci Adv (2019) 5(9), eaaw6490.

4. Cannac F., Qi C., Falschlunger J., Hausmann G., Basler K., Korkhov V.M. Cryo-EM structure of the Hedgehog release protein Dispatched. (2019) bioRxiv, doi: https://doi.org/10.1101/707513

Weinert, Adriana (Postdoc)

Vercellino,Irene (Ph.D. Student)

Graeber,Elisabeth (Ph.D. Student)

Cannac, Fabien (Ph.D Student)

Oezel, Merve (Master/Ph.D Student)