%0 Journal Article
%T Flexibility of the Cytoplasmic Domain of the Phototaxis Transducer II from Natronomonas pharaonis
%A Ivan L. Budyak
%A Olga S. Mironova
%A Naveena Yanamala
%A Vijayalaxmi Manoharan
%A Georg Bščldt
%A Ramona Schlesinger
%A Judith Klein-Seetharaman
%J Journal of Biophysics
%D 2008
%I Hindawi Publishing Corporation
%R 10.1155/2008/267912
%X 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.
%U http://www.hindawi.com/journals/jbp/2008/267912/