The periplasm is a ∼165–200 Å wide cellular compartment surrounding a gram-negative bacterium and bordered by two membranes, termed the “inner” (or cytoplasmic) and “outer” membrane. Both soluble and outer membrane proteins are secreted into the periplasm using the chemical potential of the energized inner membrane or cytoplasmic sources of ATP. However, the periplasm itself is devoid of an external energy source, yet unfolded outer membrane proteins must pass through this aqueous compartment without aggregating or misfolding. This feat is accomplished by fast and reversible interactions with soluble periplasmic chaperone proteins, a process that ensures efficient biogenesis of their outer membrane proteins clients. We are using a combination of experiments and computation to interrogate mechanistic models for this periplasmic chaperone network and find that a simultaneous consideration of all competing reactions leads to insight into the controls at work in this cellular compartment.
Karen G. Fleming (Sun,) studied this question.