Structure of a membrane-based steric chaperone in complex with its lipase substrate.

Secretion via the type II secretion pathway in Gram-negative bacteria often relies crucially on steric chaperones in the periplasm. Here, we report the crystal structure of the soluble form of a lipase-specific foldase (Lif) from Burkholderia glumae in complex with its cognate lipase. The structure reveals how Lif uses a novel α-helical scaffold to embrace lipase, thereby creating an unusually extensive folding platform.