Lubricin's Mucin Domain Has Strong Polyproline Type-II Helical Character

Area of Science:

• Biochemistry
• Structural Biology
• Biophysics

Background:

• Lubricin is a vital glycoprotein for joint health, reducing friction and preventing wear.
• It also inhibits uric acid crystal formation, thus preventing gouty arthritis.
• Limited structural data exists for lubricin's mucin domain due to its size and glycosylation.

Purpose of the Study:

• To elucidate the molecular structure of lubricin's central mucin domain.
• To understand the structural basis for lubricin's lubricating and anti-gout properties.

Main Methods:

• Physics-based replica exchange molecular dynamics (REMD) simulations.
• Circular dichroism (CD) spectroscopy experiments.

Main Results:

• REMD simulations predicted polyproline type II (PPII) helices in the mucin domain, stabilized by O-linked oligosaccharides.
• CD spectroscopy confirmed significant PPII helical content in mucin domain fragments.
• These findings elucidate the structural basis for lubricin's function.

Conclusions:

• The lubricin mucin domain exhibits substantial polyproline type II helical structure.
• This PPII structure is stabilized by glycosylation.
• The findings provide atomistic insights into lubricin's lubrication and anti-crystallization functions.