Details

Autor(en) / Beteiligte

• Bushell, Simon R.
• Mainprize, Iain L.
• Wear, Martin A.
• Lou, Hubing
• Whitfield, Chris
• Naismith, James H.

Titel

Wzi Is an Outer Membrane Lectin that Underpins Group 1 Capsule Assembly in Escherichia coli

Ist Teil von

• Structure (London), 2013-05, Vol.21 (5), p.844-853

Ort / Verlag

United States: Elsevier Inc

Erscheinungsjahr

2013

Link zum Volltext

Quelle

MEDLINE

Beschreibungen/Notizen

• Many pathogenic bacteria encase themselves in a polysaccharide capsule that provides a barrier to the physical and immunological challenges of the host. The mechanism by which the capsule assembles around the bacterial cell is unknown. Wzi, an integral outer-membrane protein from Escherichia coli, has been implicated in the formation of group 1 capsules. The 2.6 Å resolution structure of Wzi reveals an 18-stranded β-barrel fold with a novel arrangement of long extracellular loops that blocks the extracellular entrance and a helical bundle that plugs the periplasmic end. Mutagenesis shows that specific extracellular loops are required for in vivo capsule assembly. The data show that Wzi binds the K30 carbohydrate polymer and, crucially, that mutants functionally deficient in vivo show no binding to K30 polymer in vitro. We conclude that Wzi is a novel outer-membrane lectin that assists in the formation of the bacterial capsule via direct interaction with capsular polysaccharides. •Wzi is an 18-stranded β-barrel outer-membrane protein•Wzi has a unique N-terminal helical domain and novel extracellular loops•In vivo data show that extracellular loops are required for capsule formation•In vitro data show that these loops are required to bind K30 polymer Wzi is a novel β-barrel outer membrane protein that is found in bacteria that make group 1 capsules. When the protein is missing or specific regions are mutated, capsule formation is impaired. Bushell et al. show that the protein binds to K30 capsular polysaccharide and suggest it templates capsule assembly.