Solution structures of the inactive and BeF3-activated response regulator CheY2

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Sinorhizobium meliloti utilizes a chemotaxis system for flagellar motor control.
• A novel response regulator, CheY2, is involved in this signaling pathway.
• CheY2 activation by phosphorylation controls flagellar motor speed, not rotation reversal.

Purpose of the Study:

• To elucidate the structural basis of CheY2 activation and its unique motor control mechanism.
• To compare the activation mechanism of S. meliloti CheY2 with that of E. coli CheY.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy was used to determine the solution structures of inactive and activated CheY2.
• A stable analog of phosphorylated CheY2, CheY2-BeF(3), was employed to study activation-induced conformational changes.

Main Results:

• The NMR structures revealed distinct conformations for inactive and activated CheY2.
• Activation by BeF(3)(-) induced significant conformational changes, including rearrangements in the alpha4-beta5-alpha5 surface.
• Unlike E. coli CheY, S. meliloti CheY2 does not involve a Tyr-Thr-coupling mechanism for signal propagation.

Conclusions:

• The unique structural rearrangements in activated S. meliloti CheY2 create a specific binding domain for motor interaction.
• These findings explain the distinct motor speed control mechanism in S. meliloti.
• The study highlights novel response regulator activation features relevant to two-component systems.