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

Elzbieta Nowak,Santosh Panjikar,Peter Konarev,Dmitri I Svergun,Paul A Tucker

doi:10.1074/jbc.m512004200

Elzbieta Nowak, Santosh Panjikar + Show 3 more

Open Access

https://doi.org/10.1074/jbc.m512004200

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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.

Highlights

Two-component signaling (TCS) have been identified as potential antibacterial targets because they play a key role in controlling cellular processes [2]
The function and signals sensed by TCS proteins in M. tuberculosis are still poorly characterized despite their apparent importance, some initial findings have been made [5,6,7,8]
The PrrA-PrrB TCS has been implicated in the early intracellular multiplication of M. tuberculosis [9, 10]

Summary

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, little biochemical information available on the TCSs of pathogenic bacteria such as Mycobacterium tuberculosis (MtB). Response regulators all contain structurally similar N-terminal domains with a ␤1-␣1-␤2-␣2-␤3-␣3-␤4-␣4-␤5-␣5 topology that contains the conserved phosphorylation site They can be subdivided into families depending upon the expected structure of the C-terminal, or effector, domain. Structural studies investigating individual receiver domains of response regulators in their active and inactive forms provide some information about conformational changes occurring upon phosphorylation, but how this change is transmitted to activate the C-terminal effector domain is, in most cases, still a mystery. This is because structural information is much more limited in the case of intact proteins and totally absent on full-length proteins in the activated form. We show that in the crystal it exhibits a compact conformation, inhibitory for DNA binding, in solution, there is probably a percentage of a more open conformation that would be more favorable for DNA binding

EXPERIMENTAL PROCEDURES

Data collection and refinement statistics

Ramachandran plot

RESULTS AND DISCUSSION

DrrB DrrD PhoB OmpR