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PMID:21803986

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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

Significance

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


See also

References

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