Functional and Structural Characterization of RsbU, a Stress Signaling Protein Phosphatase 2C

• Published in: The Journal of biological chemistry 2004-09, Vol.279 (39), p.40927-40937
• Main Authors: Delumeau, Olivier, Dutta, Sujit, Brigulla, Matthias, Kuhnke, Grit, Hardwick, Steven W., Völker, Uwe, Yudkin, Michael D., Lewis, Richard J.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Bacillus subtilis; Bacillus subtilis - metabolism; Bacterial Proteins - chemistry; Bacterial Proteins - physiology; Crystallography, X-Ray; Dose-Response Relationship, Drug; Electrophoresis, Polyacrylamide Gel; Hydrogen Bonding; Models, Biological; Models, Molecular; Molecular Sequence Data; Phenotype; Phosphoprotein Phosphatases - chemistry; Phosphoric Monoester Hydrolases - chemistry; Phosphoric Monoester Hydrolases - metabolism; Phosphoric Monoester Hydrolases - physiology; Plasmids - metabolism; Protein Binding; Protein Conformation; Protein Phosphatase 2C; Protein Structure, Secondary; Protein Structure, Tertiary; Protein-Serine-Threonine Kinases - chemistry; Sequence Homology, Amino Acid; Signal Transduction; Time Factors
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M405464200

RsbU is a positive regulator of the activity of σB, the general stress-response σ factor of Gram+ microorganisms. The N-terminal domain of this protein has no significant sequence homology with proteins of known function, whereas the C-terminal domain is similar to the catalytic domains of PP2C-type phosphatases. The phosphatase activity of RsbU is stimulated greatly during the response to stress by associating with a kinase, RsbT. This association leads to the induction of σB activity. Here we present data on the activation process and demonstrate in vivo that truncations in the N-terminal region of RsbU are deleterious for the activation of RsbU. This conclusion is supported by comparisons of the phosphatase activities of full-length and a truncated form of RsbU in vitro. Our determination of the crystal structure of the N-terminal domain of RsbU from Bacillus subtilis reveals structural similarities to the regulatory domains from ubiquitous protein phosphatases and a conserved domain of σ-factors, illuminating the activation processes of phosphatases and the evolution of “partner switching.” Finally, the molecular basis of kinase recruitment by the RsbU phosphatase is discussed by comparing RsbU sequences from bacteria that either possess or lack RsbT.