title: Flexibility of the cytoplasmic domain of the phototaxis transducer II from Natronomonas pharaonis.
abstract: Chemo- and phototaxis systems in bacteria and archaea serve as models for more complex signal transduction mechanisms in higher eukaryotes. Previous studies of the cytoplasmic fragment of the phototaxis transducer (pHtrII-cyt) from the halophilic archaeon Natronomonas pharaonis showed that it takes the shape of a monomeric or dimeric rod under low or high salt conditions, respectively. CD spectra revealed only approximately 24% helical structure, even in 4 M KCl, leaving it an open question how the rod-like shape is achieved. Here, we conducted CD, FTIR, and NMR spectroscopic studies under different conditions to address this question. We provide evidence that pHtrII-cyt is highly dynamic with strong helical propensity, which allows it to change from monomeric to dimeric helical coiled-coil states without undergoing dramatic shape changes. A statistical analysis of predicted disorder for homologous sequences suggests that structural flexibility is evolutionarily conserved within the methyl-accepting chemotaxis protein family.
authors.affiliation: Institute for Structural Biology (IBI-2), Research Center Jülich, 52425 Jülich, Germany.
authors.forename: Ivan L
authors.initials: IL
authors.lastname: Budyak
authors.forename: Olga S
authors.initials: OS
authors.lastname: Mironova
authors.forename: Naveena
authors.initials: N
authors.lastname: Yanamala
authors.forename: Vijayalaxmi
authors.initials: V
authors.lastname: Manoharan
authors.forename: Georg
authors.initials: G
authors.lastname: Büldt
authors.forename: Ramona
authors.initials: R
authors.lastname: Schlesinger
authors.forename: Judith
authors.initials: J
authors.lastname: Klein-Seetharaman