Structure, Stability, and Function of Ion Channels and Other Membrane Proteins
Membrane proteins
– receptors, ion channels, transporters, etc. – constitute about 30% of
all proteins in eukaryotic cells. Many of them are targets for current or
future drugs. In order to facilitate the basic understanding of the biology of
these proteins and in order to aid future rational drug design improved methods
are needed to solve the structures of this class of proteins. Since membrane
proteins are harder to express and handle than soluble proteins, specialized
expression, solubilization, and stabilization techniques are required. Our
laboratory is active in all these areas and we are particularly interested in
solving structures of membrane proteins by solution NMR spectroscopy. We have
solved the very first membrane protein structure that was solved by this
technique in 2001, i.e. that of the outer membrane ion channel OmpA (see here for picture). We also performed dynamic,
thermodynamic, and electrical channel recording experiments to delineate the
gating mechanism of this ion channel. More recently in 2007, we solved the
structure of the outer membrane porin OmpG by NMR spectroscopy. This is
currently the largest membrane protein structure (33 kDa, 280 residues) ever
solved by NMR (see here for picture). The
methods that we are developing with these proteins should also be helpful to
tackle more difficult projects in the future like helical receptors and ion
channels that have been identified as potential drug targets.
Gating of OmpA ion channel
Recent
Key Publications:
Edrington, T.C. Kintz, E., Goldberg, J.B. and Tamm, L.K. (2011). Structural Basis for the Interaction of Lipopolysaccharide with the Outer Membrane Protein OprH form Pseudomonas Aeruginosa. Jour. of Biol Chem. 286, 39211-39223. (http://www.jbc.org/content/286/45/39211.full)
Liang, B., Arora, A., Tamm, L.K. “Fast-time scale dynamics of Outer membrane protein A by extended model-free analysis of NMR relaxation data” Biochim. Biophys. Acta 2010, 1798, 68-76. (http://www.ncbi.nlm.nih.gov/pubmed/19665446)
Hong,
H., Joh, N.H., Bowie, J.U., and Tamm, L.K. (2009) Methods for Measuring the
Thermodynamic Stability of Membrane Proteins. Methods in Enzymology, Vol. 455: 213-236. (http://www.ncbi.nlm.nih.gov/pubmed/19289208)
Liang
B. and Tamm, L.K. (2007) Structure of outer membrane protein G by solution NMR
spectrscopy. PNAS. Vol. 104 no.41:16140-16145. (http://www.ncbi.nlm.nih.gov/pubmed/17911261)
Hong,
H., Park, S., Flores-Jiménez, R.H., Rinehart, D., and Tamm, L.K. (2007) Role of
aromatic side chains in the folding and thermodynamic stability of integral
membrane proteins. J.A.C.S. 129:8320-8327. (http://www.ncbi.nlm.nih.gov/pubmed/17564441)
Hong
H., Szabo G., Tamm L.K. (2006) Electrostatic Coupling in OmpA Ion-Channal
Gating Suggest a Mechanism for Pore Opening. Nature Chem. Biol. Vol.2 No.11 627-635. (http://www.ncbi.nlm.nih.gov/pubmed/17041590)
Tamm
L.K., Liang B. (2006). NMR of membrane protein in solution. Prog.
in Nuc Mag Res Spec. Vol.48 201-210.
Cierpicki T., Liang B., Tamm L.K., Bushweller J.H.. (2006). Increasing the Accuracy of Solution NMR Structures of Membrane Proteins by Application of Residual Dipolar Coupling. High-Resolution Structure of Outer Membrane Protein A.. J.
Am Chem. Soc Vol.128 No.21 6947-6951. (http://www.ncbi.nlm.nih.gov/pubmed/16719475).
Liang
B., Bushweller J.H., Tamm L.K. (2006). Site-Directed Parallel Spin-Labeling and
Paramagnetic Relaxation Enhancement in Structure Determination of Membrane
Proteins by Solution NMR Spectroscopy. J. Am Chem. Soc Vol.128 No.13 4389-4397. (http://pubs.acs.org/doi/abs/10.1021/ja0574825).
Hong,
H., Patel D.R., Tamm L.K. and Berg B.V.D. (2006). The Outer Membrane Protein
OmpW Forms an Eight-stranded β-Barrel with a Hydrophobic Channel. Jour. of
Biol Chem. Vol. 281 No.11: 7568-7577. (http://www.ncbi.nlm.nih.gov/pubmed/16414958).
Tamm,
L.K., H. Hong, and B. Liang (2004). Folding and assembly of beta-barrel
membrane proteins. (Review) Biochim. Biophys. Acta. 1666: 250-263. (http://www.ncbi.nlm.nih.gov/pubmed/15519319).
Hong,
H. and L.K. Tamm (2004). Elastic coupling of integral membrane protein
stability to lipid bilayer forces. Proc. Nat. Acad. Sci. 101: 4065-4070 (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC384696/). Commentary by Dr. James Bowie (PDF).
Tamm,
L.K., F. Abildgaard, A. Arora, H. Blad, and J.H. Bushweller (2003). Structure,
dynamics and function of the outer membrane protein A (OmpA) and influenza
hemagglutinin fusion domain in detergent micelles by solution NMR. (Minireview)
FEBS Lett. 555: 139-143. (http://www.ncbi.nlm.nih.gov/pubmed/14630334)
Kleinschmidt,
J.H. and L.K. Tamm (2002). Secondary and tertiary structure formation of the
beta-barrel membrane protein OmpA is synchronized and depends on membrane
thickness. J. Mol. Biol. 324: 319-330. (http://www.ncbi.nlm.nih.gov/pubmed/12441110)
Kleinschmidt,
J.H. and L.K. Tamm (2002). Structural transitions in short-chain lipid
assemblies studied by
Arora, A. and L.K. Tamm (2001). Biophysical approaches to membrane protein structure determination. (Review) Curr. Opin. Struct. Biol. 11: 540-547.
Tamm,
L.K., A. Arora, and J.H. Kleinschmidt (2001). Structure and assembly of
beta-barrel membrane proteins. (Review) J. Biol. Chem. 276: 32399-32402.
Arora,
A., A. Frits, J.H. Bushweller, and L.K. Tamm (2001). Structure of outer
membrane protein A transmembrane domain by NMR spectroscopy. Nature Struct.
Biol. 8: 334-338. (http://www.ncbi.nlm.nih.gov/pubmed/11276254)
Arora,
A., D. Rinehart, G. Szabo, and L.K. Tamm (2000). Refolded outer membrane
protein A of Escherichia coli forms ion channels with two conductance
states in planar bilayers. J. Biol. Chem. 275:1594-1600. (http://www.ncbi.nlm.nih.gov/pubmed/10636850)
Kleinschmidt,
J.H., M. Wiener, and L.K. Tamm (1999). Outer membrane protein A of E. coli
folds into detergent micelles, but not in the presence of monomeric detergent. Protein
Sci. 8:2065-2071. (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2144138/pdf/10548052.pdf)
Kleinschmidt,
J.H. and L.K. Tamm (1999). Time-resolved distance determination by tryptophan fluorescence
quenching (TDFQ): Probing intermediates in membrane protein folding. Biochemistry 38: 4996-5005. (http://www.uni-konstanz.de/FuF/Bio/folding/bi9824644.pdf)
Kleinschmidt, J. and L.K. Tamm (1996). Folding intermediates of a beta-barrel membrane protein. Kinetic evidence for a multi-step membrane insertion mechanism. Biochemistry. 35:12993-13000. (http://www.ncbi.nlm.nih.gov/pubmed/8855933)
Rodionova,
N.A., S.A. Tatulian, T. Surrey, F. Jähnig, and L.K. Tamm (1995).
Characterization of two membrane-bound forms of OmpA. Biochemistry. 34:1921-1929. (http://www.ncbi.nlm.nih.gov/pubmed/7849052)
Tamm,
L.K. (1994) Physical studies of peptide-bilayer interactions. In Membrane
Protein Structure, Experimental Approaches. S.H. White, ed.,
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Membrane protein structure and folding | Viral membrane fusion | Synaptic membrane fusion | Supported model membranes | Key techniques |