title: Functional and structural effects of seven-residue deletions on the coiled-coil cytoplasmic domain of a chemoreceptor.
abstract: Chemoreceptors transmit signals from the environment to the flagellar motors via a histidine kinase that controls the phosphorylation level of the effector protein CheY. The cytoplasmic domain of chemoreceptors is strongly conserved and consists of a long alpha-helical hairpin that forms, in the dimer, a coiled-coil four-helix bundle. Changes in this domain during evolution are characterized by the presence of seven-residue insertions/deletions located symmetrically with respect to the hairpin turn, suggesting that specific interactions between the helices that form the hairpin are required for function. We assessed the impact of seven-residue deletions on the signalling ability and higher-order organization of the serine chemoreceptor from Escherichia coli. Our results indicate that symmetry alterations between the two branches of the cytoplasmic hairpin seriously compromise chemoreceptor function. Shorter functional versions of Tsr with symmetrical deletions form mixed trimers of dimers when coexpressed with Tar, the aspartate receptor of E. coli. However, Tar function in those cells is impaired, suggesting that the length difference between receptors introduces non-functional distortions into the chemoreceptor cluster. This observation is reinforced by the analysis of coexpression of Tar with chemoreceptors from Rhodobacter sphaeroides that naturally belong to a shorter-length class.
authors: Instituto de Investigaciones Biológicas, Universidad Nacional de Mar del Plata, Mar del Plata, Buenos Aires, Argentina.
authors: Diego A
authors: DA
authors: Massazza
authors: Silvina A
authors: SA
authors: Izzo
authors: A Florencia
authors: AF
authors: Gasperotti
authors: M Karina
authors: MK
authors: Herrera Seitz
authors: Claudia A
authors: CA
authors: Studdert
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D019281:Dimerization; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000072236:Methyl-Accepting Chemotaxis Proteins; D017434:Protein Structure, Tertiary; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D000072236:Methyl-Accepting Chemotaxis Proteins; D011956:Receptors, Cell Surface; C057331:Tar protein, E coli; C000607606:cheY protein, E coli; C000607604:tsr protein, E coli