Changing the specificity of a bacterial chemoreceptor

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Methyl-accepting chemotaxis proteins (MCPs) are crucial bacterial receptors mediating chemotaxis to various signals.
• Understanding the plasticity of these receptors is key to deciphering bacterial sensory mechanisms.

Purpose of the Study:

• To develop a method for selecting bacterial cells with altered chemotaxis responses.
• To investigate the mutational plasticity of the Escherichia coli aspartate receptor (Tar) for novel ligand detection.

Main Methods:

• A novel selection method using diffusive gradients in semi-soft agar plates was established.
• This technique allows selection for cells responding to attractants without requiring their metabolism or degradation.
• The method was applied to mutate the Tar receptor in E. coli to identify variants with altered specificities.

Main Results:

• The Tar receptor was successfully mutated to respond to new chemical signals, demonstrating significant plasticity.
• Specificity changes varied; one variant detecting cysteic acid showed broadened specificity, retaining aspartate sensitivity.
• Other variants responding to phenylalanine, N-methyl aspartate, or glutamate exhibited reduced aspartate response, with some changes not solely due to binding pocket substitutions.

Conclusions:

• The Tar receptor exhibits considerable plasticity, allowing for the engineering of new ligand specificities.
• The developed selection method provides a powerful tool for studying chemoreceptor ligand binding and signal transduction.
• These findings and techniques offer new avenues for engineering receptors for biotechnological applications.