The Structural Basis of Signal Transduction for the Response Regulator PrrA from Mycobacterium tuberculosis

Abstract

The structure of the two-domain response regulator PrrA from Mycobacterium tuberculosis shows a compact structure in the crystal with a well defined interdomain interface. The interface, which does not include the interdomain linker, makes the recognition helix and the trans-activation loop of the effector domain inaccessible for interaction with DNA. Part of the interface involves hydrogen-bonding interactions of a tyrosine residue in the receiver domain that is believed to be involved in signal transduction, which, if disrupted, would destabilize the interdomain interface, allowing a more extended conformation of the molecule, which would in turn allow access to the recognition helix. In solution, there is evidence for an equilibrium between compact and extended forms of the protein that is far toward the compact form when the protein is inactivated but moves toward a more extended form when activated by the cognate sensor kinase PrrB.The use of regulatory systems to sense and respond to changing environmental conditions is an intrinsic feature that enables bacteria to survive and adapt to a variety of external challenges. Two-component signaling (TCS) 2 systems are the principle mechanism used by bacteria to perform this task (1). A typical TCS consists of a sensor histidine kinase and a response regulator (RR). Histidine kinases are usually membrane-anchored proteins with a characteristic core consisting of a histidine-containing dimerization domain and a catalytic domain. In response to extracellular, and in a few cases, intracellular, conditions, the histidine kinase autophosphorylates at a histidine residue, usually in the dimerization domain, by phosphotransfer from the catalytic (ATPase) domain of the adjacent protomer. It then acts as a phosphodonor to a universally conserved aspartic acid residue in the response regulator. RRs typically consist of two domains with the N-terminal (receiver) domain being the phosphoacceptor domain and the C-terminal domain being the effector. The effector domain is, in most cases, DNA binding and is involved in transcriptional regulation of the genes necessary to respond to the sensed environment. Phosphorylation of the aspartic acid residue located in the receiver domain activates the effector domain in a manner that is still incompletely understood, not least because there is little structural information on full-length response regulators and no structural information on activated full-length (i.e. multidomain) response regulators.TCSs have been identified as potential antibacterial targets because they play a key role in controlling cellular processes (2). The lack of these systems in higher eukaryotes makes them potentially selective and unique antibacterial drug targets, There is, however, little biochemical information available on the TCSs of pathogenic bacteria such as Mycobacterium tuberculosis (MtB). The H37Rv strain of MtB has 12 putative TCSs including the recently discovered Rv3220-Rv1626 pair (3) as well as five putative orphan response regulator and se...

Phosphorylation of PhoP Protein Plays Direct Regulatory Role in Lipid Biosynthesis of Mycobacterium tuberculosis

“…Although M. tuberculosis PhoP regulates ϳ114 genes acting both as a transcriptional activator and repressor (5), the role of phosphorylation in transcription regulation by PhoP remains unknown. In agreement with what was evident from the structural data of M. tuberculosis PrrA (16), the closest homologue of M. tuberculosis PhoP, we recently reported inter-domain interactions in PhoP leading to phosphorylation-dependent high affinity DNA binding of the regulator (17). However, molecular mechanism of how PhoP functions as a transcriptional regulator of its target genes remains undefined.…”

Structure of the DNA-Binding Domain of the Response Regulator PhoP from Mycobacterium tuberculosis,

“…Crystal structures of full-length DrrB (24) and DrrD (25) from Thermotoga maritima indicate that in the unphosphorylated state the DNA recognition helix is freely exposed to the solvent, which would make it readily available for DNA binding. However, in the structure of PrrA from MTB, the recognition helix is involved in interactions with the regulatory domain, although in solution there may be an equilibrium with an open form (26).…”

Comparative Computational Analysis of a Putative Transcriptional Regulator Map_PRSO3010 and its implications in the Pathogenesis of Crohn’s and Johne’s diseases

“…The presence intrinsically disordered regions signify the signaling and regulatory functional role of Rv0757 and MAP_PRSO3010 proteins since the disorder region enable interactions of these proteins with proteins from multiple pathways. This leads to the upregulation and downregulation of various genes involved the virulence of Mtb in humans [45][46][47]. Both MAP_PRSO3010 and Rv0757 protein show the presence of a series of amino acids having the propensity to form alpha-helix, and also lining the pore of the transmembrane at the N-terminal and C-terminal of MAP and H37Rv bacterium.…”