Phosphorylation modulates keratin structure

Area of Science:

• Biochemistry
• Structural Biology
• Cell Biology

Background:

• Keratin serves as a crucial structural protein in intermediate filaments.
• Understanding keratin's structural dynamics is key to comprehending cellular organization.
• Post-translational modifications like phosphorylation can significantly alter protein function.

Purpose of the Study:

• To investigate the structural impact of cAMP-dependent protein kinase phosphorylation on bovine hoof keratin.
• To elucidate how phosphorylation affects keratin's rigidity and alpha-helical content.
• To explore the potential consequences of these structural changes on intermediate filament organization.

Main Methods:

• Utilized [gamma-32P]ATP to phosphorylate bovine hoof keratin.
• Employed natural-abundance cross-polarization magic-angle spinning (CP MAS) 13C NMR to assess structural changes.
• Analyzed circular dichroism (CD) spectra to determine alterations in secondary structure.
• Performed magic-angle spinning (MAS) 31P nuclear magnetic resonance (NMR) to identify phosphorylation sites.

Main Results:

• Phosphorylation increased the motionally restricted portions of keratin, indicating enhanced rigidity.
• Circular dichroism spectra suggested a potential increase in keratin's alpha-helical content post-phosphorylation.
• 31P NMR revealed distinct phosphorylation sites, with evidence of both motionally restricted and less restricted classes.
• The N-terminal region of keratin was identified as the likely site of structural alteration.

Conclusions:

• cAMP-dependent phosphorylation significantly alters bovine hoof keratin structure, increasing rigidity.
• These structural changes may lead to modifications in the intracellular organization of intermediate filaments.
• The study highlights the role of phosphorylation in regulating keratin's structural properties and cellular function.