A Myxococcus xanthus CbpB containing two cAMP-binding domains is involved in temperature and osmotic tolerances.
Our previous data indicated that a Myxococcus xanthus sensor-type adenylyl cyclase (CyaA) functions in signal transduction during osmotic stress. However, the cAMP-mediated signal transduction pathway in this bacterium was unknown. Here, we isolated a clone from a M. xanthus genomic DNA library using oligonucleotide probes designed based on the conserved cAMP-binding domains of the cAMP-dependent protein kinase (PKA) regulatory subunits. The clone contained two open-reading frames (ORFs), cbpA and cbpB, encoding hydrophilic proteins with one and two cAMP-binding domains, respectively. The CbpB exhibited partial primary structural similarity to PKA regulatory subunits. cbpA and cbpB mutants, generated by gene disruption, showed normal growth, development and spore germination. However, the cbpB mutant cultured under high- or low-temperature conditions exhibited a marked reduction in growth. cbpB mutant cells were also more sensitive to osmotic stress than wild-type cells. The cbpA mutant possessed normal resistance to such stress. The phenotype of cbpB mutant was similar to those of PKA regulatory subunit mutants of some eukaryotic microorganisms.
Kimura
Yoshio
Y
Department of Life Sciences, Faculty of Agriculture, Kagawa University, Miki-cho, Kagawa 761-0795, Japan. kimura@ag.kagawa-u.ac.jp
Nakato
Hiroshi
H
Ishibashi
Kouji
K
Kobayashi
Sousuke
S
D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004269:DNA, Bacterial / Q000235:genetics; D015870:Gene Expression; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009154:Mutation; D016941:Myxococcus xanthus / Q000235:genetics / Q000378:metabolism*; D009997:Osmotic Pressure; D017434:Protein Structure, Tertiary; D021122:Protein Subunits; D017386:Sequence Homology, Amino Acid; D013696:Temperature
D004269:DNA, Bacterial; D021122:Protein Subunits; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases