Crystal structure of the phospholipase A and acyltransferase 4 (PLAAT4) catalytic domain

Area of Science:

• Biochemistry
• Structural Biology
• Parasitology

Background:

• Phospholipase A and Acyltransferase 4 (PLAAT4) functions as a class II tumor suppressor.
• PLAAT4 restricts intracellular *Toxoplasma gondii* infection by limiting parasitic vacuole size.
• The N-terminal domain (NTD) and C-terminal domain (CTD) interaction is crucial for PLAAT4's sub-cellular targeting and enzymatic function.
• Dynamics of the NTD L1 and L2 loops regulate PLAAT4's enzymatic activity.

Purpose of the Study:

• To determine the crystal structure of the PLAAT4 NTD.
• To investigate the conformational flexibility of the L1 loop.
• To correlate crystal structure dynamics with solution NMR data.

Main Methods:

• X-ray crystallography of severely intergrown crystals.
• Automated, laser-based crystal harvesting and data reduction.
• Ensemble refinement of crystal structure data.
• Nuclear Magnetic Resonance (NMR) spectroscopy.

Main Results:

• The crystal structure of PLAAT4 NTD was determined.
• The L1 loop was observed in two distinct conformations, indicating complex interactions and flexibility.
• Ensemble refinement successfully reproduced correlated motions seen in solution NMR.
• Insights into millisecond dynamics were gained from the crystal structure.

Conclusions:

• The crystal structure provides a static snapshot of PLAAT4 NTD, revealing conformational states of the L1 loop.
• Structural flexibility of the L1 loop is influenced by a network of interactions.
• Crystal structure analysis complements NMR studies by offering insights into dynamics.
• This work enhances understanding of PLAAT4's structure-function relationship in tumor suppression and parasite restriction.