Common Patterns of Hydrolysis Initiation in P-loop Fold Nucleoside Triphosphatases

Area of Science:

• Biochemistry
• Structural Biology
• Enzymology

Background:

• P-loop fold nucleoside triphosphate (NTP) hydrolases are a large, ancient enzyme family vital in cellular processes.
• Their catalytic mechanisms remain incompletely understood, despite medical importance.
• This study addresses the lack of consensus on how these enzymes function.

Purpose of the Study:

• To clarify the catalytic mechanism of P-loop NTPases through comparative structural analysis.
• To identify common structural features essential for catalysis across diverse P-loop NTPases.
• To investigate the role of stimulatory elements in initiating gamma-phosphate hydrolysis.

Main Methods:

• Comparative structural analysis of over 3100 P-loop NTPase structures.
• Focus on structures with bound substrate Mg-NTPs or analogues.
• Analysis of interactions between catalytic site residues and the gamma-phosphate group.

Main Results:

• Identified common structural features essential for catalysis in P-loop NTPases.
• Demonstrated that specific stimulatory moieties (Arg/Lys) initiate gamma-phosphate cleavage.
• Found a conserved mechanistic interaction where stimulators rotate gamma-phosphate oxygen atoms away from the Mg ion.

Conclusions:

• The rotation of gamma-phosphate oxygen atoms, initiated by stimulatory residues, is a conserved feature crucial for P-loop NTPase catalysis.
• This rearrangement likely affects Mg ion coordination and initiates the hydrolysis mechanism.
• Results provide a foundation for understanding the catalytic mechanisms of this enzyme superfamily.