The three-dimensional structure of the ligand-binding domain of a wild-type bacterial chemotaxis receptor. Structural comparison to the cross-linked mutant forms and conformational changes upon ligand binding.
The three-dimensional structures of the ligand-binding domain of the wild-type Salmonella typhimurium aspartate receptor have been determined in the absence (apo) and presence of bound aspartate (complex) and compared to a cross-linked mutant containing a cysteine at position 36 which does not change signaling behavior of the intact receptor. The structures of the wild-type forms were determined in order to assess the effects of cross-linking on the structure and its influence on conformational changes upon ligand binding. As in the case of the cross-linked mutant receptor, the non-cross-linked ligand-binding domain is dimeric and is composed of 4-alpha-helical bundle monomer subunits related by a crystallographic 2-fold axis in the unbound form and by a non-crystallographic axis in the aspartate-bound form. A comparative study between the non-cross-linked and cross-linked structures has led to the following observations: 1) The long N-terminal helices of the individual subunits in the cross-linked structures are bent toward each other to accommodate the disulfide bond. 2) The rest of the subunit conformation is very similar to that of the wild-type. 3) The intersubunit angle of the cross-linked apo structure is larger by about 13 degrees when compared to the wild-type apo structure. 4) The nature and magnitude of the aspartate-induced conformational changes in the non-cross-linked wild-type structures are very similar to those of the cross-linked structures.
Yeh
J I
JI
Department of Chemistry, Lawrence Berkeley Laboratory, University of California, Berkeley 94720.
Biemann
H P
HP
Pandit
J
J
Koshland
D E
DE
Kim
S H
SH
D000595:Amino Acid Sequence; D001059:Apoproteins / Q000737:chemistry / Q000378:metabolism; D001224:Aspartic Acid / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D002628:Chemoreceptor Cells; D003432:Cross-Linking Reagents; D029968:Escherichia coli Proteins; D008024:Ligands; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016296:Mutagenesis; D017433:Protein Structure, Secondary; D017459:Receptors, Amino Acid / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011956:Receptors, Cell Surface; D012486:Salmonella typhimurium / Q000378:metabolism*
D001059:Apoproteins; D001426:Bacterial Proteins; D003432:Cross-Linking Reagents; D029968:Escherichia coli Proteins; D008024:Ligands; D046911:Macromolecular Substances; D008565:Membrane Proteins; D017459:Receptors, Amino Acid; D011956:Receptors, Cell Surface; C057331:Tar protein, E coli; C031959:aspartic acid receptor; D001224:Aspartic Acid