C-Mannosylation Enhances the Structural Stability of Human RNase 2

Area of Science:

• Biochemistry
• Glycobiology
• Structural Biology

Background:

• C-mannosylation is a rare protein glycosylation where an α-mannopyranosyl residue attaches to the indole ring of tryptophan.
• This modification was first identified in RNase 2 and is found in various significant proteins.

Purpose of the Study:

• To investigate the conformational dynamics of C-mannosylated glycopeptides and RNase 2.
• To elucidate the role of C-mannosylation in protein structure stabilization and dynamics.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy
• Molecular Dynamics (MD) simulations (hundreds of microseconds)
• Analysis of both isolated glycopeptides and native/denatured RNase 2

Main Results:

• In isolated glycopeptides and denatured RNase 2, the C-linked mannopyranosyl residue adopts a dynamic ensemble of conformations, with the ¹C₄ conformation being most prevalent.
• In native RNase 2, the mannopyranosyl residue favors a specific conformation.
• This favored conformation in native RNase 2 forms stabilizing hydrogen bonds and significantly reduces protein dynamics on the microsecond timescale.

Conclusions:

• C-mannosylation plays a crucial role in stabilizing protein structure.
• The conformational state of the C-linked mannose residue is dependent on the protein's native or denatured state.
• Understanding C-mannosylation's impact on protein dynamics offers insights into its biological functions.