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19 January 2006 Elucidating the structure and function of S100 proteins in membranes
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S100 proteins are important Ca2+-binding proteins involved in vital cellular functions including the modulation of cell growth, migration and differentiation, regulation of intracellular signal transduction/phosphorylation pathways, energy metabolism, cytoskeletal interactions and modulation of ion channels. Furthermore, they are implicated in oncogenesis and numerous other disease states. Three S100 proteins: S100A8, S100A9 and S100A12 are constitutively expressed in neutrophils and monocytes. At low levels of intracellular Ca2+, S100A8 and S100A9 are located predominantly in the cytosol but when Ca2+ concentrations are elevated as a consequence of activation, they translocate to membranes and complex with cytoskeletal components such as vimentin. The functions of S100A8 and S100A9 at the plasma membrane remain unclear. A possible role may be the regulation of ion channel proteins. The current study uses the techniques of Atomic Force Microscopy and production of artificial lipid membranes in the form of liposomes to investigate possible mechanisms for the insertion of these proteins into membranes in order to elucidate their structure and stoichiometry in the transmembrane state. We have successfully imaged the liposomes as a lipid bilayer, the S100A8/A9 protein complex in solution and the S100A8/A9 complex associating with lipid, using tapping-mode atomic force microscopy, in buffer.
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Stella M. Valenzuela, Mark Berkahn, Donald K. Martin, Thuan Huynh, Zheng Yang, and Carolyn L. Geczy "Elucidating the structure and function of S100 proteins in membranes", Proc. SPIE 6036, BioMEMS and Nanotechnology II, 603619 (19 January 2006);

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