1. Structure of a Membrane Proteins in Situ F. Jamilidinan, P. Schwander,D. K. Saldin

2. TechniqueImportance RESEARCH Future SCENE

3. Why our work is important and what is our goal?  The targets of most medicinal drugs are membrane proteins  They are very difficult to crystallize  x-ray crystallography – trillions of molecules in identical orientations – not possible with most membrane proteins.  Can we work with partial alignment?  Ion channel proteins tend to be positioned within an membrane with random angles perpendicular to the membrane  However, their angular correlations are independent of particle orientation  Can we exploit this fact for structure determination?  The targets of most medicinal drugs are membrane proteins  They are very difficult to crystallize  x-ray crystallography – trillions of molecules in identical orientations – not possible with most membrane proteins.  Can we work with partial alignment?  Ion channel proteins tend to be positioned within an membrane with random angles perpendicular to the membrane  However, their angular correlations are independent of particle orientation  Can we exploit this fact for structure determination? 1 Solvent annulus Bilayer Incident x-rays Membrane Protein OUR TECHNIQUE  A collection of randomly oriented molecules give rise to a DP that looks angularly featureless.  However, the correlated scattering from each particle is the same.  The correlated signal tends to be drowned in the much larger uncorrelated signal from different molecules.  Assuming we can separate the signals, we exploit an algorithm for reconstructing a DP from its angular correlations.  Having reconstructed a single particle DP can get the projected potential by an iterative phasing algorithm  A collection of randomly oriented molecules give rise to a DP that looks angularly featureless.  However, the correlated scattering from each particle is the same.  The correlated signal tends to be drowned in the much larger uncorrelated signal from different molecules.  Assuming we can separate the signals, we exploit an algorithm for reconstructing a DP from its angular correlations.  Having reconstructed a single particle DP can get the projected potential by an iterative phasing algorithm 2 Why our work is important and what is our goal?  The targets of medicinal drugs are membrane proteins  Very difficult to crystallize => x-ray crystallography  The ion channel proteins tend to be positioned with random angles about this axis  We suggest a novel technique of determining the structures of membrane proteins in such configurations  The targets of medicinal drugs are membrane proteins  Very difficult to crystallize => x-ray crystallography  The ion channel proteins tend to be positioned with random angles about this axis  We suggest a novel technique of determining the structures of membrane proteins in such configurations 1 OUR TECHNIQUE 1.Generating simulated diffraction patterns from 10 randomly positioned and oriented model K- channel protein 2.recovery of a single-particle diffraction pattern from many particles diffraction patterns 3.Recovery of the projected electron density of a single particle 1.Generating simulated diffraction patterns from 10 randomly positioned and oriented model K- channel protein 2.recovery of a single-particle diffraction pattern from many particles diffraction patterns 3.Recovery of the projected electron density of a single particle 2 Future  Can overcome bottleneck for determining atomic scale structures of membrane proteins.  Will lead to a greater understanding of the action of medicinal drugs and perhaps other phenomena that depend on membrane proteins, such as photosynthesis  Can overcome bottleneck for determining atomic scale structures of membrane proteins.  Will lead to a greater understanding of the action of medicinal drugs and perhaps other phenomena that depend on membrane proteins, such as photosynthesis 3