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Membrane Protein Structure Overview present and future

Membrane Protein Structure Overview present and future. D.C. Rees Caltech/HHMI. Membrane Proteins - Interests and Challenges participate in transport and transduction processes that mediate the flow of matter, energy and information across the membrane bilayer

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Membrane Protein Structure Overview present and future

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  1. Membrane Protein Structure Overview • present and future D.C. Rees Caltech/HHMI

  2. Membrane Proteins - Interests and Challenges participate in transport and transduction processes that mediate the flow of matter, energy and information across the membrane bilayer are poorly characterized relative to water-soluble proteins due to experimental challenges of mimicking the membrane and water-bilayer interfaces constitute an estimated ~20% of all proteins, yet only ~40 distinct structures are available membrane protein structure websites: http://blanco.biomol.uci.edu/Membrane_Proteins_xtal.html http://www.mpibp-frankfurt.mpg.de/michel/public/memprotstruct.html

  3. membrane protein abundances 15-30% total, 10-20% > 2 TM Liu & Rost Prot. Sci.10, 1970 (2001)

  4. Membrane protein structure: Status bioenergetic systems photosynthetic reaction centers (bacterial, PSI, PSII) bacteriorhodopsin (BR, HR, SR) respiratory complexes (II, III, IV and V) FDH, NarGHI light harvesting complexes ADP/ATP carrier transporters Ca+2 ATPase AcrB ABC transporters (MsbA, BtuCD) MFS (LacY, GlpT) channels/receptors K+ (KcsA, MthK, KirBac1.1, KvAP) mechanosensitive (MscL, MscS) aquaporins (GlpT, AQP) ClC AchR rhodopsin b-barrel 8,10,12,14,16,18,22 b-strands

  5. Structural analysis of membrane proteins natural sources or cloning & expression (recombinant) solubilization (detergents) purification crystallization structure determination

  6. 10-30 homologs membrane protein crystallization: approaches detergents/additives - RC lipidic phases - BR Fab complexes - cytochrome c oxidase proteolysis - KcsA sequence engineering - OmpX homologues - MscL

  7. BtuCD structure determination 3.2 Å resolution Locher et al. Science 296, 1091 (2002)

  8. BtuCD: molecular architecture of an ABC transporter two-fold NCS BtuC BtuC periplasm cytoplasm BtuC BtuD

  9. surface polarity of membrane proteins reflects the solvent environment

  10. surface hydrophobicity profile for membrane proteins ARBB31, 207 (2002) Nagle & Tristram-Nagle, COSB10, 474 (2000)

  11. endpoints of transmembrane helices

  12. helix tilt and helix-helix crossing angle distributions average tilt = 23˚ + 10˚ ARBB31, 207 (2002)

  13. Hydrophobicities of buried/surface residues membrane proteins vs water-soluble proteins TM region, 16 a-helical mps buried / surface Asp Ile +1 -1 0 hydrophobicity surface buried water-soluble proteins Eisenberg et al. hydrophobicity scale Faraday Symp. Chem. Soc.17, 109 (1982) Science 245, 510 (1989) ARBB31, 207 (2002)

  14. Membrane protein - water-soluble protein comparison water membrane membrane proteins and water soluble proteins have similar interior apolarities packing densities surface areas stabilities (?) and differ in surface polarities helix-helix packing distributions tertiary folds what is the role of solvent in defining protein structures?

  15. B.W. Matthews Ann. Rev. Phys. Chem.27, 493 (1976) http://www.mpibp-frankfurt.pg.de/ michel/public/memprotstruct.html photosynthetic reaction center myoglobin progress in membrane protein structure determinations parallels that of water-soluble proteins with a ~25 year offset

  16. “Should we designate a certain percentage of targets to membrane proteins and/or protein complexes?” YES!!! Membrane protein challenges: overexpression of eukaryotic proteins solubilization (detergents) state-specific stabilizers

  17. Acknowledgments (~t-20 years to present) RC: J. Allen, T. Yeates, A. Chirino, A. Yeh, H. Axelrod, G. Feher FRD: T. Iverson, C. Luna-Chavez, G. Cecchini MscL: G. Chang, R. Spencer, A. Lee, M. Barclay, R. Bass, P. Strop, J. Choe, S. Steinbacher MscS: R. Bass, P. Strop, M. Barclay, Y. Poon BtuCD: K. Locher, A. Lee, L. Borths general: R. Spencer, L. DeAntonio, D. Eisenberg

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