PMID:21803986

Citation	Kitanovic, S, Ames, P and Parkinson, JS (2011) Mutational analysis of the control cable that mediates transmembrane signaling in the Escherichia coli serine chemoreceptor. J. Bacteriol. 193:5062-72
Abstract	During transmembrane signaling by Escherichia coli Tsr, changes in ligand occupancy in the periplasmic serine-binding domain promote asymmetric motions in a four-helix transmembrane bundle. Piston displacements of the signaling TM2 helix in turn modulate the HAMP bundle on the cytoplasmic side of the membrane to control receptor output signals to the flagellar motors. A five-residue control cable joins TM2 to the HAMP AS1 helix and mediates conformational interactions between them. To explore control cable structural features important for signal transmission, we constructed and characterized all possible single amino acid replacements at the Tsr control cable residues. Only a few lesions abolished Tsr function, indicating that the chemical nature and size of the control cable side chains are not individually critical for signal control. Charged replacements at I214 mimicked the signaling consequences of attractant or repellent stimuli, most likely through aberrant structural interactions of the mutant side chains with the membrane interfacial environment. Prolines at residues 214 to 217 also caused signaling defects, suggesting that the control cable has helical character. However, proline did not disrupt function at G213, the first control cable residue, which might serve as a structural transition between the TM2 and AS1 helix registers. Hydrophobic amino acids at S217, the last control cable residue, produced attractant-mimic effects, most likely by contributing to packing interactions within the HAMP bundle. These results suggest a helix extension mechanism of Tsr transmembrane signaling in which TM2 piston motions influence HAMP stability by modulating the helicity of the control cable segment.
Links	PubMed PMC3187437 Online version:10.1128/JB.05683-11
Keywords	Bacterial Proteins/chemistry; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Cell Membrane/metabolism; Chemotaxis/genetics; Chemotaxis/physiology; DNA Mutational Analysis/methods; Escherichia coli/genetics; Escherichia coli/metabolism; Escherichia coli/physiology; Membrane Proteins/chemistry; Membrane Proteins/genetics; Membrane Proteins/metabolism; Models, Biological; Protein Structure, Secondary; Protein Structure, Tertiary; Signal Transduction/genetics; Signal Transduction/physiology
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
ECOLI:MCP1		GO:0060286: flagellar cell motility	ECO:0000315:		P		Figure 3	complete CACAO 5842
ECOLI:MCP1		GO:0006935: chemotaxis	ECO:0000315:		P		Figure 2: shows mutant chemotaxis phenotypes	complete CACAO 5841
ECOLI:MCP1		GO:0007165: signal transduction	ECO:0000315:		P		Fig. 4 shows examples of tsr control cable mutants signaling defects. See also Fig 7.	complete CACAO 5840
ECOLI:MCP1		GO:0008984: protein-glutamate methylesterase activity	ECO:0000315:		F		Fig 1 shows methylation sites indicating glutamine residues that must be deamidated to glutamates	complete CACAO 5043
ECOLI:MCP1		GO:0048870: cell motility	ECO:0000315:		P		Figure 2 and 5 show motility through chemotaxis	complete CACAO 5906
ECOLI:MCP1	involved_in	GO:0006935: chemotaxis	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete
ECOLI:MCP1	involved_in	GO:0007165: signal transduction	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete
ECOLI:MCP1	involved_in	GO:0048870: cell motility	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete

References

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