The bindosome is a structural component of the Sulfolobus solfataricus cell envelope

Area of Science:

• Microbiology
• Biochemistry
• Archaea research

Background:

• Thermoacidophile Sulfolobus solfataricus utilizes sugar binding proteins and ABC transporters for sugar uptake.
• These proteins are synthesized with class III signal peptides, similar to archaeal flagellins and bacterial type IV pilins.
• Cell surface expression relies on the bindosome assembly system (Bas), homologous to bacterial type IV pilin assembly.

Purpose of the Study:

• To investigate the role of the Bas system in sugar binding protein function and cell morphology in S. solfataricus.
• To characterize the composition and assembly of the Bas system and its interaction with cell surface structures.

Main Methods:

• Genetic complementation of a S. solfataricus ΔbasEF strain with BasEF and an ATPase mutant of BasE.
• Detergent extraction of BasEF complex from S. solfataricus membranes.
• Extraction of cell surface solute binding proteins into high molecular mass complexes.
• Electron microscopic analysis of wild-type and ΔbasEF strains.

Main Results:

• Expression of BasEF restored glucose uptake in the ΔbasEF strain, while an ATPase mutant failed to complement.
• BasEF was isolated as a stable detergent-extracted complex from membranes.
• Solute binding proteins formed 600 and 400 kDa complexes, with the larger one including the S-layer protein SlaA.
• Absence of BasEF altered cell morphology and S-layer pattern, which was reversed by complementation.

Conclusions:

• The Bas system is essential for functional cell surface sugar uptake in S. solfataricus.
• The Bas system interacts with the S-layer protein (SlaA), influencing cell morphology and S-layer organization.
• This interaction highlights a novel role for the Bas system beyond sugar transport, impacting archaeal cell shape.