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PAS/poly-HAMP signalling in Aer-2, a soluble haem-based sensor
Kylie J Watts1, Barry L Taylor, Mark S Johnson
1Division of Microbiology and Molecular Genetics, Loma Linda University, Loma Linda, CA 92350, USA. kwatts@llu.edu
Molecular Microbiology
|January 25, 2011
Summary
Pseudomonas aeruginosa Aer-2, a chemoreceptor with multiple HAMP domains, mediates repellent responses. Ligand binding to the PAS domain and specific HAMP domains regulate its kinase activity.
Area of Science:
- Microbiology
- Structural Biology
- Biochemistry
Background:
- Poly-histidine-affinity-tag (HAMP) domains are common in bacterial chemoreceptors, but their function in multi-domain proteins is understudied.
- The Pseudomonas aeruginosa chemoreceptor Aer-2 possesses a unique structure with five HAMP domains and a PAS sensing domain.
Purpose of the Study:
- To investigate the signaling mechanism and poly-HAMP domain function of the Aer-2 chemoreceptor.
- To elucidate the role of Aer-2 in Pseudomonas aeruginosa chemotaxis.
Main Methods:
- Utilized a heterologous system by expressing Aer-2 in Escherichia coli to study its function.
- Determined ligand binding properties of the Aer-2 PAS domain using spectroscopic methods.
- Investigated the role of individual HAMP domains through deletion mutagenesis.
Main Results:
- Aer-2 mediates repellent responses to oxygen, carbon monoxide, and nitric oxide when reconstituted in E. coli.
- The PAS domain of Aer-2 binds penta-coordinated b-type heme.
- Reversible signaling necessitates four of the five HAMP domains, with specific N-terminal and C-terminal HAMP domains exhibiting opposing effects on kinase activity.
Conclusions:
- A model is proposed where ligand-bound Aer-2 PAS and N-terminal HAMP domains (HAMP 2 and 3) relieve inhibition mediated by C-terminal HAMP domains (HAMP 4 and 5), activating the kinase.
- This study provides novel insights into the structure-function relationship of poly-HAMP domains in bacterial chemoreception.
