Shape and oligomerization state of the cytoplasmic domain of the phototaxis transducer II from Natronobacterium pharaonis.
Phototaxis allows archaea to adjust flagellar motion in response to light. In the photophobic response of Natronobacterium pharaonis, light-activated sensory rhodopsin II causes conformational changes in the transducer II protein (pHtrII), initiating the two-component signaling system analogous to bacterial chemotaxis. pHtrII's cytoplasmic domain (pHtrII-cyt) is homologous to the cytoplasmic domains of eubacterial chemotaxis receptors. Chemotaxis receptors require dimerization for activity and are in vivo-organized in large clusters. In this study we investigated the oligomerization and aggregation states of pHtrII-cyt by using chemical cross-linking, analytical gel-filtration chromatography, and small-angle neutron scattering. We show that pHtrII-cyt is monomeric in dilute buffers, but forms dimers in 4 M KCl, the physiological salt concentration for halophilic archaea. At high ammonium sulfate concentration, the protein forms higher-order aggregates. The monomeric protein has a rod-like shape, 202 A in length and 14.4 A in diameter; upon dimerization the length increases to 248 A and the diameter to 18.2 A. These results suggest that under high salt concentration the shape and oligomerization state of pHtrII-cyt are comparable to those of chemotaxis receptors.
Budyak
Ivan L
IL
Institute for Structural Biology and Institute of Solid-State Research, Research Center Juelich, 52425 Juelich, Germany.
Pipich
Vitaliy
V
Mironova
Olga S
OS
Schlesinger
Ramona
R
Zaccai
Giuseppe
G
Klein-Seetharaman
Judith
J
D019843:Archaeal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001704:Biopolymers / Q000737:chemistry; D002338:Carotenoids / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D003432:Cross-Linking Reagents / Q000737:chemistry; D018360:Crystallography, X-Ray; D019281:Dimerization; D008027:Light; D019633:Natronobacterium / Q000737:chemistry* / Q000378:metabolism; D010316:Particle Size; D052817:Phototrophic Processes / Q000502:physiology; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary
D019843:Archaeal Proteins; D001704:Biopolymers; D003432:Cross-Linking Reagents; C434450:phototaxis receptor sensory rhodopsin II, Natronobacterium pharaonis; D002338:Carotenoids