On Going Research Support:
RO1 GM43919 Khan (PI) 4/1/00 – 3/31/04
NIH
Bacterial Chemotaxis Probed by Photo-released Ligands.
The grants aims to understand, through characterization by computer-assisted motion analysis of chemotactic responses triggered by photo-release of the amino acid attractants serine and aspartate, and of the repellent, leucine; the mechanisms controlling timing and amplification of the chemotactic signal.
Role: PI

RO1 GM36936 Khan (PI) 4/1/01 – 3/31/05
NIH
Motility and Chemo-sensing in Bacteria.
Aims during the current period were to determine the stoichiometries of the 5 motor proteins, to map their spatial distribution onto the flagellar basal body and to characterize their functional interactions by electron microscopy and optical methods. Planned work in this competitive continuation will continue to address these goals based on the advances made.
Role: PI

Eisenbach (PI) 9/01/01-8/31/04
U.S-Israel Bi-national Science Foundation
Mechanism of Switching the Direction of Rotation in Bacterial Chemotaxis.
This grant aims to determine the co-operativity and other properties of the bacterial flagellar motor switch through measurement of optical signals generated by interactions of gfp-fusions of CheY, FliM and FliG and their change during chemotactic signaling initiated by photorelease of caged chemoeffectors.
Role:Co-Investigator

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Completed Research Support:
DBL-976770 Khan (PI) 10/1/99- 7/31/02
National Science Foundation
Evanescent Wave Polarized Fluorescence Microscopy of Bio-molecular Assemblies.
This grant develops a polarized evanescent-wave fluorescence microscope for study of the rotational dynamics of bio-molecular assemblies. In addition to measurement of bacterial flagellar rotation, this microscope will be used, in collaboration with the group of Dr R. Cross, also at SUNY Upstate Biochemistry & Molecular Biology, to measure the rotation of F0F1 ATPase, labeled with fluorescent tags at defined position on the various subunits. It will also be used to explore, in collaboration with the group of Dr M. Garcia Blanco, an MBL colleague, processive rotation of the T7 polymerase motor during translocation along DNA.
Role: PI

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Selected Publications:

1. Trewhella, J., Anderson, S., Fox, R., Gogol. E., Khan, S., Zaccai, G., and Engelman, D.M. 1983. Assignment of segments of bacteriorhodopsin sequence to positions in the structural map. Biophys. J. 42, 233-241.
2. Khan, S., and Berg, H.C. 1983. Isotope and thermal effects in chemi-osmotic coupling to the flagellar motor of Streptococcus. Cell 32, 913-919.
3. Khan, S., and Berg, H.C. 1983. Isotope and thermal effects in chemi-osmotic coupling to the membrane ATPase of Streptococcus. J. Biol. Chem. 258, 6709-6712.4. Khan, S., Meister, M., and Berg. H.C. 1985. Constraints on flagellar rotation. J. Mol. Biol. 184, 645-656.
4. Khan, S., Dapice, M., and Reese. T.S. 1988. Effects of mot gene expression on the structure of the flagellar motor. J. Mol. Biol. 202, 575-584.
5. Khan, S., Dapice, M., and Humayun, I. 1990. Energy transduction in the bacterial flagellar motor: Effects of load and pH. Biophys. J. 57, 779-796.
6. Liu, J-Z., Dapice, M., and Khan, S. 1990. Ion selectivity of the Vibrio alginolyticus flagellar motor. J. Bacteriol. 172, 5336-5244.
7. Schnapp, B.J., Crise, B., Sheetz, M.P., Reese, T.S., and Khan, S. 1990. Delayed start-up of kinesin-driven
microtubule gliding following inhibition by adenosine 5'-[b,d-imido]triphosphate. Proc. Nat. Acad. Sci. 87, 10053-10057.
8. Khan, S., Humayun Khan, I., and Reese, T.S. 1991. New structural features of the flagellar base in Salmonella typhimurium revealed by rapid-freeze electron microscopy. J. Bacteriol. 173, 2888-2896.
9. Khan, S., Amoyaw, K., Spudich, J.L., Reid, G.P., and Trentham, D.R. 1992. Bacterial chemoreceptor signalling probed by flash photorelease of a caged serine. Biophys. J. 62, 67-68.
10. Khan, I.H., Reese, T.S., and Khan, S. 1992. The cytoplasmic component of the bacterial flagellar motor. Proc. Nat. Acad. Sci. 89, 5956-5960.
11. Khan, S., Ivey, D.M., and Krulwich, T.A. 1992. Membrane ultrastructure of alkaliphilic Bacillus species studied by rapid-freeze electron microscopy. J. Bacteriol. 173, 2888-2896.
12. Khan, S., Castellano, F., Spudich, J.L., McCray, J.A., Goody, R.S., Reid, G.P., and Trentham, D.R. 1993. Excitatory signaling in bacteria probed by caged chemoeffectors. Biophys. J. 65, 2368-2382.
13. Stahlberg, A., Schuster, S., Bauer, M., Bauerlein, E., Zhao, R., Reese, T.S., and Khan, S. 1995. Conserved machinery of the bacterial flagellar motor. Biophys. J. 168-172s.
14. Khan, S., Spudich, J.L., McCray, J.A., and Trentham, D.R. 1995. Chemotactic signal integration in bacteria. Proc. Nat. Acad. Sci. 92, 9757-9761.
15. Zhao, R., Schuster, S., and Khan, S. 1995. Structural effects of mutations in Salmonella typhimurium flagellar switch complex. J. Mol. Biol. 251, 400-412.
16. Wang, Z., Khan, S., and Sheetz, M.P. 1995. Single cytoplasmic dynein molecule movements: characterization and comparison with kinesin. Biophys. J. 69, 2011-2023.
17. Zhao, R., Amsler, C.D., Matsumura, P. and Khan, S. 1996. FliG and FliM distribution in the Salmonella typhimurium Cell and Flagellar Basal Bodies. J. Bacteriol.178, 258-265.
18. Zhao, R., Pathak, N., Jaffe, H. Reese, T.S. and Khan, S. 1996. FliN is a major structural protein of the C-ring in the Salmonella typhimurium flagellar basal body. J. Mol. Biol. 261, 195-208.
19. Khan, S., Zhao, R., and Reese, T.S. 1998. Architectural features of the Salmonella typhimurium flagellar motor switch revealed by disrupted C-rings. J. Struct. Biol. 122, 311-319.
20. Jasuja, R., Keyoung, J., Reid, G.P., Trentham, D.R., and Khan, S. 1999. Chemotactic responses of
Escherichia coli to small jumps of photoreleased aspartate. Biophys. J. 76, 1706-1719.
21. Lux, R., Munasinghe, R., Castellano, F., Lengeler, J., Corrie, J.E.T., and Khan, S. 1999. Elucidation of a PTS-carbohydrate chemotactic signal pathway using a time-resolved behavioral assay. Mol Biol. Cell.10, 1133-1146.
22. Jasuja, R., Lin, Y., Trentham, D.R., and Khan, S. 1999. Response tuning in bacterial chemotaxis. Proc. Nat. Acad. Sci. 96, 11346-11351.
23. Khan, S. 2000. On bacterial tactic response times and latencies. Biophys. J. 78,2186-2187.
24. Lux, R., Kar, N., and Khan, S. 2000. Overproduced S. typhimurium flagellar motor switch complexes. J. Mol. Biol. 298, 577-584.
25. Khan, S., Pierce, D., and Vale, R.D. 2000. Interactions of the chemotaxis signal protein CheY with bacterial flagellar motors visualized by evanescent wave microscopy. Curr. Biol. 10, 927-930.
26. Kim, S., Jackson, M., Lux, R., and Khan, S. 2001. Determinants of chemotactic signal amplification in Escherichia coli. J. Mol. Biol. 307, 119-135.
27. Young, H.S., Dang, H, Lai, Y., DeRosier, D. J., and Khan, S. 2003. Variable Symmetry in Salmonella typhimurium Flagellar Motors. Biophys. J. 84, 571-577.
28. Sagi, Y., Khan, S., Eisenbach, M. 2003. Binding of the Chemotaxis Response Regulator CheY to Isolated, Intact Switch Complex of the Bacterial Flagellar Motor. The Journal of Biological Chemistry. 278, 25867-25871.