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Flexibility of the Cytoplasmic Domain of the Phototaxis Transducer II from Natronomonas pharaonis

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Author(s): Ivan L. Budyak | Olga S. Mironova | Naveena Yanamala | Vijayalaxmi Manoharan | Georg Büldt | Ramona Schlesinger | Judith Klein-Seetharaman

Journal: Journal of Biophysics
ISSN 1687-8000

Volume: 2008;
Date: 2008;
Original page

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.

Tango Jona
Tangokurs Rapperswil-Jona

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