Flexibility of the cytoplasmic domain of the phototaxis transducer II from Natronomonas pharaonis.
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.
Budyak
Ivan L
IL
Institute for Structural Biology (IBI-2), Research Center Jülich, 52425 Jülich, Germany.
Mironova
Olga S
OS
Yanamala
Naveena
N
Manoharan
Vijayalaxmi
V
Büldt
Georg
G
Schlesinger
Ramona
R
Klein-Seetharaman
Judith
J