Biomaterial Database

Features of Rhodobacter sphaeroides ChrR required for stimuli to promote the dissociation of σ(E)/ChrR complexes. 2011

Roger Greenwell, and Tae-Wook Nam, and Timothy J Donohue

Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA.

In the photosynthetic bacterium Rhodobacter sphaeroides, a transcriptional response to the reactive oxygen species singlet oxygen ((1)O(2)) is mediated by ChrR, a zinc metalloprotein that binds to and inhibits the activity of the alternative σ factor σ(E). We provide evidence that (1)O(2) promotes the dissociation of σ(E) from ChrR to activate transcription in vivo. To identify what is required for (1)O(2) to promote the dissociation of σ(E)/ChrR complexes, we analyzed the in vivo properties of variant ChrR proteins with amino acid changes in conserved residues of the C-terminal cupin-like domain (ChrR-CLD). We found that (1)O(2) was unable to promote the detectable dissociation of σ(E)/ChrR complexes when the ChrR-CLD zinc ligands (His141, His143, Glu147, and His177) were substituted with alanine, even though individual substitutions caused a 2-fold to 10-fold decrease in zinc affinity for this domain relative to that for wild-type ChrR (K(d)∼4.6×10(-)(10) M). We conclude that the side chains of these invariant residues play a crucial role in the response to (1)O(2). Additionally, we found that cells containing variant ChrR proteins with single amino acid substitutions at Cys187 or Cys189 exhibited σ(E) activity similar to those containing wild-type ChrR when exposed to (1)O(2), suggesting that these thiol side chains are not required for (1)O(2) to induce σ(E) activity in vivo. Finally, we found that the same aspects of R. sphaeroides ChrR needed for a response to (1)O(2) are required for the dissociation of σ(E)/ChrR complexes in the presence of the organic hydroperoxide t-butyl hydroperoxide.

UI	MeSH Term	Description	Entries
D008958	Models, Molecular	Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures.	Molecular Models,Model, Molecular,Molecular Model
D011485	Protein Binding	The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.	Plasma Protein Binding Capacity,Binding, Protein
D003067	Coenzymes	Small molecules that are required for the catalytic function of ENZYMES. Many VITAMINS are coenzymes.	Coenzyme,Enzyme Cofactor,Cofactors, Enzyme,Enzyme Cofactors,Cofactor, Enzyme
D005786	Gene Expression Regulation	Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control (induction or repression) of gene action at the level of transcription or translation.	Gene Action Regulation,Regulation of Gene Expression,Expression Regulation, Gene,Regulation, Gene Action,Regulation, Gene Expression
D001426	Bacterial Proteins	Proteins found in any species of bacterium.	Bacterial Gene Products,Bacterial Gene Proteins,Gene Products, Bacterial,Bacterial Gene Product,Bacterial Gene Protein,Bacterial Protein,Gene Product, Bacterial,Gene Protein, Bacterial,Gene Proteins, Bacterial,Protein, Bacterial,Proteins, Bacterial
D012242	Rhodobacter sphaeroides	Spherical phototrophic bacteria found in mud and stagnant water exposed to light.	Rhodopseudomonas sphaeroides,Rhodobacter spheroides,Rhodopseudomonas spheroides
D012808	Sigma Factor	A protein which is a subunit of RNA polymerase. It effects initiation of specific RNA chains from DNA.	Sigma Element,Sigma Initiation Factor,Sigma Subunit,Minor Sigma Factor,RNA Polymerase Sigma Factor H,Factor, Sigma,Factor, Sigma Initiation,Initiation Factor, Sigma,Sigma Factor, Minor,Subunit, Sigma
D014157	Transcription Factors	Endogenous substances, usually proteins, which are effective in the initiation, stimulation, or termination of the genetic transcription process.	Transcription Factor,Factor, Transcription,Factors, Transcription
D014158	Transcription, Genetic	The biosynthesis of RNA carried out on a template of DNA. The biosynthesis of DNA from an RNA template is called REVERSE TRANSCRIPTION.	Genetic Transcription
D015032	Zinc	A metallic element of atomic number 30 and atomic weight 65.38. It is a necessary trace element in the diet, forming an essential part of many enzymes, and playing an important role in protein synthesis and in cell division. Zinc deficiency is associated with ANEMIA, short stature, HYPOGONADISM, impaired WOUND HEALING, and geophagia. It is known by the symbol Zn.