2l9g
From Proteopedia
Solution structure of AS1p-Tar in 10% negatively charged bicelles
Structural highlights
FunctionMCP2_ECOLI Receptor for the attractant L-aspartate and related amino and dicarboxylic acids. Tar also mediates taxis to the attractant maltose via an interaction with the periplasmic maltose binding protein. Tar mediates taxis away from the repellents cobalt and nickel. Chemotactic-signal transducers respond to changes in the concentration of attractants and repellents in the environment, transduce a signal from the outside to the inside of the cell, and facilitate sensory adaptation through the variation of the level of methylation. Attractants increase the level of methylation while repellents decrease the level of methylation, the methyl groups are added by the methyltransferase CheR and removed by the methylesterase CheB. Publication Abstract from PubMedHAMP domains convert an extracellular sensory input into an intracellular signaling response in a wide variety of membrane-embedded bacterial proteins. These domains are almost invariably found adjacent to the inner leaflet of the cell membrane. We therefore examined the interaction of peptides corresponding to either AS1 or AS2 of four different, well-characterized HAMP domains with several membrane model systems. The proteins included an Archaeoglobus fulgidus protein (Af1503), the Escherichia coli osmosensor EnvZ(Ec), the E. coli nitrate/nitrite sensor NarX(Ec), and the aspartate chemoreceptor of E. coli (Tar(Ec)). Far-UV CD and NMR spectroscopy were used to monitor the induction of secondary structure upon association with neutral or acidic large unilamellar vesicles (LUVs) and bicelles. We observed significant increases in alpha-helicity within AS1 from NarX(Ec) and Tar(Ec) but not in AS1 from the other proteins. To characterize these interactions further, we determined the solution structure of AS1 from Tar(Ec) associated with acidic bicelles. The bulk of AS1 formed an amphipathic alpha-helix, whereas the N-terminal control cable, the region between TM2 and AS1, remained unstructured. We observed that the conserved prolyl residue found in AS1 of many membrane-adjacent HAMP domains defined the boundary between the unstructured and helical regions. In addition, two positively charged residues that flank the hydrophobic surface of AS1 are thought to facilitate electrostatic interactions with the membrane. We interpret these results within the context of the helix-interaction model for HAMP signaling and propose roles for AS1-membrane interactions during the membrane assembly and transmembrane communication of HAMP-containing receptors. Structural characterization of AS1-membrane interactions from a subset of HAMP domains.,Unnerstale S, Maler L, Draheim RR Biochim Biophys Acta. 2011 Oct;1808(10):2403-12. Epub 2011 Jul 6. PMID:21763270[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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