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PULSe Home > Faculty Members A-C > William Cramer
William A. Cramer
Current Research Interests:
Structure-function of integral membrane proteins, particularly those involved in energy transduction and traffic across the membrane, proton and electron transfer, protein import, and ion channels.
Structure-Function of Membrane Proteins I. Structure-Function of the Cytochrome b6f Complex
Although there are approximately 50,000 independent structures of soluble proteins, and somewhat more than 150 independent structures of integral membrane proteins (IMP) in the Protein Data Bank, there are only about 2 dozen structures of hetero-oligomeric integral membrane proteins that have been solved to a resolution d 3.0 Å. Although these membrane proteins are of great interest in health and disease-related studies, most of these hetero-oligomeric structures are of protein complexes that function in energy transducing membranes. A high resolution (3.0 Å) structure in the presence of Cd2+ ion has been obtained of one of the three major hetero-oligomeric membrane protein complexes, the cytochrome b6f complex, in the electron transport chain of oxygenic photosynthesis.Photosynthetic_electron_transport
The dimeric 220 kDa complex in cyanobacteria contains 8 polypeptide subunits (Science, 302, 1009-, 2003; Ann. Rev. Biochem., 75, 769-, 2006, J. Mol. Biol., 370: 59-72, 2007), 13 trans-membrane helices, and 7 prosthetic groups (4 hemes, 1 FeS cluster, 1 Chl a, 1 beta-carotene) per monomer. Several aspects of this structure complex are novel, including the single chlorophyll a, beta-carotene, and unique covalently bound heme cn, which is 5-coordinate, with a water as the 5th ligand, but unique without any amino acid side chain to serve as an axial ligand. Crystal structures with quinone analogue inhibitors imply that heme cn is the electron donor to plastoquinone on the n- or stromal side of the membrane. The structures provide insight into the pathways of electron and H + transport, and also describe the labyrinthine transfer pathways of the hydrophobic plastoquinone and -quinol across the b6f complex.
II. Protein Import:The Colicin Translocon
Concept for the pathway and mechanisms of import into E. coli of the cytotoxic E colicins are based on structures of the outer membrane vitamin B12 receptor (BtuB; panels A, B, side and top views; J. Mol. Biol. 364: 716-734, 2006) and OmpF translocator (see below, E; EMBO J., 27, 2171-2180, 2008) which the colicins parasitize for their import. A 2.75 Å structure of the complex of the receptor-binding domain of the endoribonucleolytic colicin E3 (panel C) showed the elongate 100 Å long colicin domain to be bound in an oblique mode, in which it can fish for a second (OmpF) outer membrane translocator (Nat Struct Biol, 10, 948-954, 2003 ). A very similar structure was obtained for a complex of the receptor-binding domain of colicin E2 and BtuB (panel D) [J. Biol. Chem., 282: 2171-2180]. Circular dichroism in the far UV has been used to characteracterize the "unfolded" secondary structure of the N- and C-terminal peptides of colicin E3 that interact with the outer membrane receptors, BtuB and OmpF (Biochemistry, 45, 10199-, 2006). III. Discrete Ion Channel Formation by Alpha-Synuclein
Alpha-Synuclein, a 140 amino acid cytosolic protein (Fig. below), implicated in the pathogenesis of Parkinson's Disease (PD), can exert its cellular function through interaction with membranes. This interaction has been studied mostly with oligomeric or aggregated "protofibrillar" forms of synuclein. In contrast to the view prevalent in the literature that the membrane-interactive form of alphaSynuclein is the oligomeric beta-stranded form that permeabilizes membranes, studies that we have carried out with J. - C. Rochet showed that monomeric synuclein in an alpha-helical conformation formed specific ion channels in planar bilayer membranes having a physiological lipid composition (Zakharov et al., Biochemistry, 2007). These channels, formed by insertion into the membrane bilayer, must result from the formation of a trans-membrane helical dimer or higher order oligomer. The synuclein trans-membrane channels could have a positive function in the metabolism of synaptic membranes through transport of biogenic amines.
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Selected Publications:
Baniulis, D., H. Zhang, T. Zakharova, and W. A. Cramer. 2009. Purification and Crystallization of the Cytochrome b6f Complex in Oxygenic Photosynthesis; in Methods in Molecular Biology, Photosynthesis Research Protocols (Ed., R. Carpentier), Humana Press Inc, Totowa, NJ. in press.
Cramer, W. A., E. Yamashita, D. Baniulis, and S. S. Hasan. 2009. The Cytochorme b6f Complex of Oxygenic Photosynthesis in The Handbook of Metallopproteins (A. Messerschmidt, ed.), J. Wiley, Chichester. in press.
Twigg, A. I., Baniulis, W. A., Cramer, W. A., Hendrich, M. P. 2009. EPR Detection of an O2 Surrogate Bound to Heme cn of the Cytochrome b6f Complex. J. Amer. Chem Soc. in press.
Baniulis, D., E. Yamashita, J.P. Whitelegge, A. Zatsman, M.P. Hendrich, and W.A. Cramer. 2009. Structure-function and stability of the cyanobacterial cytochrome b6f complex from Nostoc sp. PCC 7120. J. Biol. Chem. 284, 9861-9869.
Sharma, O., K. A. Datsenko, S. C. Ess, M. V. Zhalnina, B. L. Wanner, and W. A. Cramer. 2009. Genome-wide screens: novel mechanisms in colicin import and cytotoxicity. Molecular Microbiology. 73: 571-585.
Yan, J., N. Dashdorj, D. Baniulis, E. Yamashita, S. Savikhin and W. A. Cramer. 2008. On the Structural Role of the Aromatic Residue Environment of the Chlorophyll a in the Cytochrome b6f Complex. Biochemistry. 47: 3654-3661.
Yamashita, E., Zhalnina, M. V., Zakharov, S. D., Sharma, O., Cramer, W. A. 2008. Crystal structures of the OmpF porin: function in a colicin translocon. Embo J. 27: 2171-2180.
Zakharov, S. D., Hulleman, J. D., Dutseva, E. A., Antonenko, Y. N., Rochet, J. C., Cramer, W. A. 2007. Helical alpha ±-Synuclein Forms Highly Conductive Ion Channels. Biochemistry. 46: 14369-14379.
Baniulis, D., E. Yamashita, H. Zhang, S. S. Hasan, and W. A. Cramer. 2008. Structure-Function of the Cytochrome b6f Complex. Photochemistry and Photobiology. 84: 1349-1358.
Zakharov, S. D., O. Sharma, O., M. Zhalnina, and W. A. Cramer. 2008. Primary Events in the Colicin Translocon: FRET Analysis of Colicin Unfolding Initiated by Binding to BtuB and OmpF. Biochemistry. 47: 12802-12809.
Cramer, W. A, D. Baniulis, E. Yamashita, H. Zhang, A.I. Zatsman, M.P. Hendrich. 2008. Structure, spectroscopy, and function of the cytochrome b6f complex: heme cn and n-side electron and proton transfer reactions; in Photosynthetic Protein Complexes. A Structural Approach (P. Fromme, ed.). Wiley-VCH, Weinheim. 155-179.
Dashdorj, N., Yamashita, E., Schaibley, J., Cramer, W. A., Savikhin, S. 2007. Ultrafast Optical Pump-Probe Studies of the Cytochrome b6f Complex in Solution and Crystalline States. J Phys Chem B. 111: 14405-14410.
Sharma, O., Cramer, W. A. 2007. Minimum length requirement of the flexible N-terminal translocation subdomain of colicin E3. J Bacteriol. 189: 363-368.
Sharma, O., Yamashita, E., Zhalnina, M. V., Zakharov, S. D., Datsenko, K. A., Wanner, B. L., Cramer, W. A. 2007. Structure of the complex of the colicin E2 R-domain and its BtuB receptor. The outer membrane colicin translocon. J Biol Chem. 282: 23163-23170.
Yamashita, E., Zhang, H., Cramer, W. A. 2007. Structure of the cytochrome b6f complex: quinone analogue inhibitors as ligands of heme cn. J Mol Biol. 370: 39-52.
Adams, K. L., Tsoi, S., Yan, J., Durbin, S. M., Ramdas, A. K., Cramer, W. A., Sturhahn, W., Alp, E. E., Schulz, C. 2006. Fe vibrational spectroscopy of myoglobin and cytochrome f. 110: 530-536.
Cherezov, V., Yamashita, E., Liu, W., Zhalnina, M., Cramer, W. A., Caffrey, M. 2006. In meso structure of the cobalamin transporter, BtuB, at 1.95 A resolution. J Mol Biol. 364: 716-734.
Cramer, W. A., Zhang, H. 2006. Consequences of the structure of the cytochrome b6f complex for its charge transfer pathways. Biochim Biophys Acta. 1757: 339-345.
Cramer, W. A., Zhang, H., Yan, J., Kurisu, G., Smith, J. L. 2006. Transmembrane traffic in the cytochrome b(6)f complex. Annu Rev Biochem. 75: 769-790.
Sobko, A. A., Kotova, E. A., Antonenko, Y. N., Zakharov, S. D., Cramer, W. A. 2006. Lipid dependence of the channel properties of a colicin E1-lipid toroidal pore. J Biol Chem. 281: 14408-14416.
Sobko, A. A., Kotova, E. A., Zakharov, S. D., Cramer, W. A., Antonenko, Y. N. 2006. Lipid-mediated inactivation of colicin e1 channels by calcium ions. Biochemistry (Mosc). 71: 99-103.
Whitelegge, J. P., Laganowsky, A., Nishio, J., Souda, P., Zhang, H., Cramer, W. A. 2006. Sequencing covalent modifications of membrane proteins. J Exp Bot. 57: 1515-1522.
Yan, J., Kurisu, G., Cramer, W. A. 2006. Intraprotein transfer of the quinone analogue inhibitor 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone in the cytochrome b6f complex. Proc Natl Acad Sci U S A. 103: 69-74.
Zakharov, S. D., Zhalnina, M. V., Sharma, O., Cramer, W. A. 2006. The colicin E3 outer membrane translocon: immunity protein release allows interaction of the cytotoxic domain with OmpF porin. Biochemistry. 45: 10199-10207.
Zatsman, A. I., Zhang, H., Gunderson, W. A., Cramer, W. A., Hendrich, M. P. 2006. Heme-heme interactions in the cytochrome b6f complex: EPR spectroscopy and correlation with structure. J Am Chem Soc. 128: 14246-14247.
Cramer, W. A., Yan, J., Zhang, H., Kurisu, G., Smith, J. L. 2005. Structure of the cytochrome b6f complex: new prosthetic groups, Q-space, and the hors doeuvres hypothesis for assembly of the complex. Photosynth Res. 85: 133-143.
Cramer, W. A., Zhang, H., Yan, J., Kurisu, G. 2005. Binding sites of lipophilic quinone and quinone analogue inhibitors in the cytochrome b6f complex of oxygenic photosynthesis. Biochem Soc Trans. 33: 921-923.
Dashdorj, N., Zhang, H., Kim, H., Yan, J., Cramer, W. A., Savikhin, S. 2005. The single chlorophyll a molecule in the cytochrome b6f complex: unusual optical properties protect the complex against singlet oxygen. Biophys J. 88: 4178-4187.
Genji, K., Zakharov, S. D., Zhalnina, M. V., Cramer, W. A. 2005. Molecular mechanism of protein import through receptor complexes: implication of the complex structure of outer membrane receptor and colicin E3. Tanpakushitsu Kakusan Koso. 50: 356-361.
Kim, H., Dashdorj, N., Zhang, H., Yan, J., Cramer, W. A., Savikhin, S. 2005. An anomalous distance dependence of intraprotein chlorophyll-carotenoid triplet energy transfer. Biophys J. 89: L28-30.
Zhang, H., Cramer, W. A. 2005. Problems in obtaining diffraction-quality crystals of hetero-oligomeric integral membrane proteins. J Struct Funct Genomics. 6: 219-223.
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