The C-terminal head domain of Burkholderia pseudomallei BpaC has a striking hydrophilic core with an extensive...

Area of Science:

• Structural biology
• Microbiology
• Biochemistry

Background:

• Gram-negative pathogens utilize trimeric autotransporter adhesins (TAAs) for virulence.
• BpaC from Burkholderia pseudomallei is a key adhesin involved in pathogenicity.

Purpose of the Study:

• To determine the high-resolution crystal structure of the membrane-proximal BpaC head domain.
• To analyze the unique structural features of the BpaC head domain.
• To compare BpaC with other known parallel β-roll structures.

Main Methods:

• 1.4 Å X-ray crystallography of the BpaC head domain.
• Comparative analysis of protein structures and surface charge distribution.

Main Results:

• The BpaC head domain is composed exclusively of left-handed parallel β-roll repeats, representing the largest structure of its kind solved.
• Unusual hydrophilic residues (Threonine and Asparagine) form the core, creating distinct solvent channels.
• The BpaC head domain exhibits a negatively charged surface, contrasting with the positively charged surface of YadA.

Conclusions:

• The unique structural characteristics of the BpaC head domain warrant its classification as a distinct subtype.
• The position and charge distribution of head domains may influence the function of trimeric autotransporter adhesins.
• This research provides insights into the structural diversity and functional implications of β-roll domains in bacterial pathogens.