Oxford University Department of Biochemistry
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Catherine Vénien-Bryan
Electron microscopy of signalling proteins

Co-workers: Ms Brittany Zadek, Madeleine Dorthe

Many signals in the cell are conveyed by interacting protein molecules. How do protein-protein interactions lead to a response? The most likely explanation is through changes in structure. We study protein-protein interactions in the control of signalling processes using electron microscopy and combining the results with information from X-ray diffraction studies.
The regulation of the flow of potassium ions into cells is important in the propagation of the neuronal action potential, cell volume regulation and muscle contraction. Potassium channels are controlled by pore gating : the channel can exist in either an open or a closed state. We are testing a hypothesis for the conformational response by imaging the channel in the two states.

Protein phosphorylation catalysed by protein kinases is a widespread mechanism for control of events in the cell. Phosphorylase kinase is a key enzyme in the control of glycogen metabolism. This complex is strictly regulated by hormonal messengers (adrenaline), neuronal stimuli (Ca2+) and metabolic pathway (ADP). The electron microscopy studies should improve our understanding of the arrangement of the protein subunits in one of the most complex protein kinases.
Image analysis of 2D crystals using cryo-electron microscopy can bring structural information at very high resolution. Unfortunately it is often difficult to produce large and well ordered 2D crystals. We are developing and testing new techniques and strategies for crystallizing soluble and membrane proteins in 2D, either on a lipid monolayer or on a preformed scaffolding.


Research Images

Figure 1: Projection map of KirBac3.1, a potassium channel, from frozen 2D crystals. Closed and open conformations.

Figure 2: Overview of proposed gating motions in KirBac3.1

Figure 3: Electron micrograph of negatively stained phosphorylase kinase.The scale bar equals 300Å

Figure 4: Cryo-EM study: surface representation of phosphosphorylase kinase at 9Å resolution calculated from 87000 frozen particles

Contact: catherine.venien@bioch.ox.ac.uk

Graduate Student and Postdoctoral Positions: Enquiries with CV welcome

Website: http://biop.ox.ac.uk/www/lj2005/contents.html

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