title: The YjbH protein of Bacillus subtilis enhances ClpXP-catalyzed proteolysis of Spx.
abstract: The global transcriptional regulator Spx of Bacillus subtilis is controlled at several levels of the gene expression process. It is maintained at low concentrations during unperturbed growth by the ATP-dependent protease ClpXP. Under disulfide stress, Spx concentration increases due in part to a reduction in ClpXP-catalyzed proteolysis. Recent studies of Larsson and coworkers (Mol. Microbiol. 66:669-684, 2007) implicated the product of the yjbH gene as being necessary for the proteolytic control of Spx. In the present study, yeast two-hybrid analysis and protein-protein cross-linking showed that Spx interacts with YjbH. YjbH protein was shown to enhance the proteolysis of Spx in reaction mixtures containing ClpXP protease but not ClpCP protease. An N-terminal truncated form of YjbH with a deletion of residues 1 to 24 (YjbH(Delta1-24)) showed no proteolysis enhancement activity. YjbH is specific for Spx as it did not accelerate proteolysis of the ClpXP substrate green fluorescent protein (GFP)-SsrA, a GFP derivative with a C-terminal SsrA tag that is recognized by ClpXP. Using inductively coupled plasma atomic emission spectroscopy and 4-(2-pyridylazo) resorcinol release experiments, YjbH was found to contain zinc atoms. Zinc analysis of YjbH(Delta1-24) revealed that the N-terminal histidine-rich region is indispensable for the coordination of at least one Zn atom. A Zn atom coordinated by the N-terminal region was rapidly released from the protein upon treatment with a strong oxidant. In conclusion, YjbH is proposed to be an adaptor for ClpXP-catalyzed Spx degradation, and a model of YjbH redox control involving Zn dissociation is presented.
authors.affiliation: Division of Environmental and Biomolecular Systems, Department of Science and Engineering, School of Medicine, Oregon Health and Science University, Beaverton, Oregon 97006, USA.
authors.forename: Saurabh K
authors.initials: SK
authors.lastname: Garg
authors.forename: Sushma
authors.initials: S
authors.lastname: Kommineni
authors.forename: Luke
authors.initials: L
authors.lastname: Henslee
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
authors.forename: Peter
authors.initials: P
authors.lastname: Zuber
mesh_terms: D001412:Bacillus subtilis / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D049071:Endopeptidase Clp / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D010084:Oxidation-Reduction; D010447:Peptide Hydrolases / Q000378:metabolism; D011485:Protein Binding; D015032:Zinc / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D010447:Peptide Hydrolases; D049071:Endopeptidase Clp; D015032:Zinc