N-Glycosylation Is Important for Proper Haloferax volcanii S-Layer Stability and Function

Area of Science:

• Microbiology
• Biochemistry
• Structural Biology

Background:

• N-glycosylation, the attachment of sugars to proteins, is common in archaea, but its function is unclear.
• The surface layer (S-layer) glycoprotein is the sole component of the S-layer in *Haloferax volcanii*.
• Understanding archaeal N-glycosylation is crucial for comprehending diverse biological processes.

Purpose of the Study:

• To investigate the impact of N-glycosylation on the structure and physiology of *Haloferax volcanii*.
• To elucidate the role of N-glycosylation in S-layer assembly and function.
• To determine how N-glycosylation affects S-layer glycoprotein conformation and secretion processes.

Main Methods:

• Cryo-electron microscopy of membrane vesicles from wild-type and N-glycosylation mutant strains.
• Analysis of reporter protein secretion in parent and mutant strains.
• Protease susceptibility assays to assess S-layer glycoprotein conformation.

Main Results:

• Perturbed N-glycosylation led to incomplete S-layer coverage on membrane vesicles.
• Compromised N-glycosylation impaired the secretion of a reporter protein across the S-layer.
• Mutants lacking specific glycosyltransferases exhibited altered S-layer glycoprotein conformation and increased protease susceptibility.

Conclusions:

• N-glycosylation is essential for proper S-layer assembly and integrity in *Haloferax volcanii*.
• Altered N-glycosylation affects protein secretion and S-layer glycoprotein folding.
• *Haloferax volcanii* may modulate N-glycosylation to adapt its S-layer architecture and function to environmental changes.