The three-dimensional structure of the aspartate receptor fromEscherichia coli

Abstract

The crystal structure of the periplasmic domain of the aspartate receptor from Escherichia coli has been solved and refined to an R-factor of 0.203 at 2.3 A, resolution. The dimeric protein is largely helical, with four helices from each monomer forming a four-helix bundle. The dimer interface is constructed from four helices, two from each subunit, also packed together in a four-helix bundle arrangement. A sulfate ion occupies the aspartate-binding site. All hydrogen bonds made to aspartate are substituted by direct or water-mediated hydrogen bonds to the sulfate. Comparison of the Escherichia coli aspartate-receptor structure with that of Salmonella typhimurium [Milburn, Prive, Milligan, Scott, Yeh, Jancarik, Koshland & Kim (1991). Science, 254, 1342-1347; Scott, Milligan, Milburn, Prive, Yeh, Koshland & Kim (1993). J. Mol. Biol. 232, 555-573] reveals strong conservation in the structure of the monomer, but more divergence in the orientation of the subunits with respect to one another. Mutations that render the Escherichia coli receptor incapable of responding to maltose are either located in spatially conserved sites or in regions of the structures that have high temperature factors and are therefore likely to be quite flexible. The inability of the receptor from Salmonella typhimurium to respond to maltose may, therefore, be because of differences in amino acids located on the binding surface rather than structural differences.

Structure of a conserved receptor domain that regulates kinase activity: the cytoplasmic domain of bacterial taxis receptors

“…All of the MTP receptors for which structural information exists are family A chemoreceptors from the homologous chemotaxis pathways of E. coli and S. typhimurium [1••,2••, 4,7,[15][16][17][18][19][20][21][22][23][24][25][26][27]. These chemoreceptors are homodimers and possess a large periplasmic domain formed by the association of two identical, antiparallel four-helix bundles, one from each subunit [15][16][17][18][19].…”

“…These chemoreceptors are homodimers and possess a large periplasmic domain formed by the association of two identical, antiparallel four-helix bundles, one from each subunit [15][16][17][18][19]. The transmembrane region is a single antiparallel four-helix bundle formed by the pairing of two membrane-spanning α helices from each subunit [20][21][22][23][24][25][26][27].…”

THE TWO-COMPONENT SIGNALING PATHWAY OF BACTERIAL CHEMOTAXIS: A Molecular View of Signal Transduction by Receptors, Kinases, and Adaptation Enzymes

“…This homodimeric fragment, consisting of two 19-kDa subunits, includes virtually the entire periplasmic region of the receptor and retains the native ligandbinding properties even though the transmembrane helices have been removed (Milligan & Koshland 1993, Danielson et al 1994. Crystallographic structures of the isolated domain reveal that each subunit is an antiparallel four-helix bundle in which the individual helices are labeled α1 through α4, yielding a roughly cylindrical dimeric domain approximately 20 Å in diameter and 70 Å in length (Figure 7) (Milburn et al 1991, Bowie et al 1995, Yeh et al 1996. Two symmetric aspartate-binding sites are located at the interface of the two subunits, near the extreme periplasmic end of the domain.…”

Evidence that the Adaptation Region of the Aspartate Receptor Is a Dynamic Four-Helix Bundle: Cysteine and Disulfide Scanning Studies

“…The structures of the periplasmic and transmembrane regions are wellcharacterized, with each dominated by four-helix bundles (23)(24)(25). In the periplasmic domain, helices α1-4 of each subunit form a four-helix bundle, and the two symmetric bundles associate at the dimer interface dominated by an α1-α1′ coiled-coil interaction.…”