Molecular basis of C-mannosylation - a structural perspective.

Area of Science:

• Biochemistry
• Structural Biology
• Glycobiology

Background:

• Post-translational modifications (PTMs) diversify protein structure and function.
• C-mannosylation, a rare PTM, involves attaching D-mannopyranose to tryptophan residues via a carbon-carbon bond.
• Understanding C-mannosylation is limited, with few 3D structures available.

Purpose of the Study:

• To conduct the first comprehensive review of C-mannosylated protein structures.
• To analyze structural data for all 10 proteins with C-mannosylation in the RCSB PDB.
• To identify conserved motifs and residues associated with C-mannosylation.

Main Methods:

• Analysis of structural data from the RCSB Protein Data Bank (PDB).
• Detailed examination of the WXXW/WXXWXXW consensus motif.
• Investigation of conserved arginine residues and C-terminal PXP motifs.

Main Results:

• Identification of conserved WXXW/WXXWXXW motifs and arginine residues at C-mannosylation sites.
• Discovery of a conserved PXP motif C-terminal to the C-mannosylation site, forming a tight turn.
• Demonstration of C-mannopyranosyl group stabilization via hydrogen bonding with arginine and other polar residues.

Conclusions:

• Conserved structural features, including WXXW motifs, arginine residues, and PXP sequences, are critical for C-mannosylation.
• C-mannosylation influences protein stability, secretion, and function.
• Further research using advanced structural biology techniques is needed to uncover novel C-mannosylation pathways and functions.