Crystal structure of SAM-dependent methyltransferase from Pyrococcus horikoshii

Area of Science:

• Biochemistry
• Structural Biology
• Enzymology

Background:

• Methyltransferases (MTs) are vital enzymes catalyzing methylation, essential for cellular functions like gene expression and metabolism.
• SAM-dependent methyltransferases (SAM-MTs) utilize the cofactor S-adenosyl-L-methionine (SAM) for their catalytic activity.

Purpose of the Study:

• To determine the crystal structure of Pyrococcus horikoshii SAM-MT.
• To elucidate the structural basis of SAM-MT function and cofactor binding.

Main Methods:

• X-ray diffraction was employed to determine the crystal structure.
• High-resolution structural analysis was performed at 2.1 Å.

Main Results:

• The Pyrococcus horikoshii SAM-MT exhibits a monomeric structure composed of a Rossmann-like fold (domain I) and a substrate-binding domain (domain II).
• The cofactor SAM binds at the interface between enzyme subunits, suggesting proximity to the active site.
• The enzyme was observed to exist in a dimeric state.

Conclusions:

• The dimeric state of Pyrococcus horikoshii SAM-MT is likely important for its catalytic function.
• Structural insights into SAM-MTs can inform the understanding of methylation processes and enzyme mechanisms.