Isolation and functional analysis of a gene, tcsB, encoding a transmembrane hybrid-type histidine kinase from Aspergillus nidulans.
We cloned and characterized a novel Aspergillus nidulans histidine kinase gene, tcsB, encoding a membrane-type two-component signaling protein homologous to the yeast osmosensor synthetic lethal N-end rule protein 1 (SLN1), which transmits signals through the high-osmolarity glycerol response 1 (HOG1) mitogen-activated protein kinase (MAPK) cascade in yeast cells in response to environmental osmotic stimuli. From an A. nidulans cDNA library, we isolated a positive clone containing a 3,210-bp open reading frame that encoded a putative protein consisting of 1,070 amino acids. The predicted tcsB protein (TcsB) has two probable transmembrane regions in its N-terminal half and has a high degree of structural similarity to yeast Sln1p, a transmembrane hybrid-type histidine kinase. Overexpression of the tcsB cDNA suppressed the lethality of a temperature-sensitive osmosensing-defective sln1-ts yeast mutant. However, tcsB cDNAs in which the conserved phosphorylation site His(552) residue or the phosphorelay site Asp(989) residue had been replaced failed to complement the sln1-ts mutant. In addition, introduction of the tcsB cDNA into an sln1delta sho1delta yeast double mutant, which lacked two osmosensors, suppressed lethality in high-salinity media and activated the HOG1 MAPK. These results imply that TcsB functions as an osmosensor histidine kinase. We constructed an A. nidulans strain lacking the tcsB gene (tcsBdelta) and examined its phenotype. However, unexpectedly, the tcsBdelta strain did not exhibit a detectable phenotype for either hyphal development or morphology on standard or stress media. Our results suggest that A. nidulans has more complex and robust osmoregulatory systems than the yeast SLN1-HOG1 MAPK cascade.
Furukawa
Kentaro
K
Laboratory of Enzymology, Department of Molecular and Cell Biology, Graduate School of Agricultural Science, Tohoku University, 1-1 Amamiya, Tsutsumi-dori, Sendai 981-8555, Japan.
Katsuno
Yasuaki
Y
Urao
Takeshi
T
Yabe
Tomio
T
Yamada-Okabe
Toshiko
T
Yamada-Okabe
Hisafumi
H
Yamagata
Youhei
Y
Abe
Keietsu
K
Nakajima
Tasuku
T
D000595:Amino Acid Sequence; D001233:Aspergillus nidulans / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D005800:Genes, Fungal; D000071677:Histidine Kinase; D008565:Membrane Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism / Q000502:physiology; D008969:Molecular Sequence Data; D009994:Osmolar Concentration; D011494:Protein Kinases / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism / Q000502:physiology; D017386:Sequence Homology, Amino Acid
D008565:Membrane Proteins; D011494:Protein Kinases; D000071677:Histidine Kinase; C469334:TcsB protein, Aspergillus nidulans