Structural basis of response regulator dephosphorylation by Rap phosphatases

Area of Science:

• Microbiology
• Structural Biology
• Biochemistry

Background:

• Bacterial Rap proteins regulate key cellular processes like sporulation.
• Rap phosphatases dephosphorylate the Spo0F response regulator, controlling sporulation in Bacillus species.
• The mechanism of Rap phosphatase activity was previously undefined.

Purpose of the Study:

• To elucidate the structural and mechanistic basis of Rap protein phosphatase activity on Spo0F.
• To identify critical residues and interactions governing Rap-Spo0F dephosphorylation.
• To enable prediction of Spo0F phosphatase activity based on Rap protein sequence.

Main Methods:

• X-ray crystallography of RapH-Spo0F complex.
• Biochemical assays to assess phosphatase activity.
• Genetic studies to validate functional interactions.
• Protein engineering to modify Rap protein function.

Main Results:

• The RapH-Spo0F crystal structure reveals a 3-helix bundle and tetratricopeptide repeat domain.
• A catalytic glutamine in RapH's 3-helix bundle is crucial for Spo0F dephosphorylation.
• RapH antagonizes sporulation by blocking phosphoryl transfer to/from Spo0F.
• Structure-function analysis identified key residues for Spo0F phosphatase activity.
• Spo0F phosphatase activity can now be assigned to Rap proteins based on sequence.
• A non-phosphatase Rap protein was engineered to dephosphorylate Spo0F.

Conclusions:

• The study reveals the mechanistic basis of Spo0F dephosphorylation by Rap proteins.
• Rap proteins utilize a conserved catalytic glutamine and interact with Spo0F's active site.
• Rap proteins can inhibit sporulation through both dephosphorylation and steric hindrance.
• The findings support the T-loop-Y allostery model of receiver domain regulation.