The source of high signal cooperativity in bacterial chemosensory arrays
| Autor: | John S. Parkinson, Vered Frank, Germán E. Piñas, Ady Vaknin |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
0301 basic medicine
Multidisciplinary Escherichia coli Proteins 030106 microbiology Allosteric regulation Histidine kinase Wild type Cooperativity Biological Sciences Biology Transmembrane protein Cell membrane 03 medical and health sciences 030104 developmental biology medicine.anatomical_structure Biochemistry Escherichia coli Mutagenesis Site-Directed Biophysics medicine Kinase activity Receptor |
| Zdroj: | Proceedings of the National Academy of Sciences. 113:3335-3340 |
| ISSN: | 1091-6490 0027-8424 |
| DOI: | 10.1073/pnas.1600216113 |
| Popis: | The Escherichia coli chemosensory system consists of large arrays of transmembrane chemoreceptors associated with a dedicated histidine kinase, CheA, and a linker protein, CheW, that couples CheA activity to receptor control. The kinase activity responses to receptor ligand occupancy changes can be highly cooperative, reflecting allosteric coupling of multiple CheA and receptor molecules. Recent structural and functional studies have led to a working model in which receptor core complexes, the minimal units of signaling, are linked into hexagonal arrays through a unique interface 2 interaction between CheW and the P5 domain of CheA. To test this array model, we constructed and characterized CheA and CheW mutants with amino acid replacements at key interface 2 residues. The mutant proteins proved defective in interface 2-specific in vivo cross-linking assays, and formed signaling complexes that were dispersed around the cell membrane rather than clustered at the cell poles as in wild type chemosensory arrays. Interface 2 mutants down-regulated CheA activity in response to attractant stimuli in vivo, but with much less cooperativity than the wild type. Moreover, mutant cells containing fluorophore-tagged receptors exhibited greater basal anisotropy that changed rapidly in response to attractant stimuli, consistent with facile changes in loosely packed receptors. We conclude that interface 2 lesions disrupt important network connections between core complexes, preventing receptors from operating in large, allosteric teams. This work confirms the critical role of interface 2 in organizing the chemosensory array, in directing the clustered array to the cell poles, and in producing its highly cooperative signaling properties. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|