Chaperone function of FkpA, a heat shock prolyl isomerase, in the periplasm ofEscherichia coli

Abstract

SummaryThe nature of molecular chaperones in the periplasm of Escherichia coli that assist newly translocated proteins to reach their native state has remained poorly defined. Here, we show that FkpA, a heat shock periplasmic peptidyl-prolyl cis/trans isomerase (PPIase), suppresses the formation of inclusion bodies from a defective-folding variant of the maltose-binding protein, MalE31. This chaperone-like activity of FkpA, which is independent of its PPIase activity, requires a full-length structure of the protein. In vitro, FkpA does not catalyse a slow rate-limiting step in the refolding of MalE31, but prevents its aggregation at stoichiometric amounts and promotes the reactivation of denaturated citrate synthase. We propose that FkpA functions as a chaperone for envelope proteins in the bacterial periplasm.

Interaction of FkpA, a peptidyl-prolylcis/transisomerase with EspP autotransporter protein

“…8,9 Pet, Sat, SigA and EspC have shown to be cytotoxic to was shown to reduce the σ E -dependent response induced by misfolded proteins in the periplasm, 33 suppress the formation of inclusion bodies from a defective maltosebinding protein and promote the reactivation of denatured citrate synthase. 20 Our previous work showed that secretion of EspP was dramatically reduced in a DegP mutant strain; however, overexpression of the SurA or FkpA proteins significantly improved the EspP secretion in this mutant.…”

“…36 We assume that FkpA would fit in the SurA pathway since both have similar functions, beside their chaperoning role, SurA and FkpA have also shown PPIase activity. 20,37 On the other hand, YaeT, a component of the Bam complex, was also found solution through the flow cell under continuous flow. In this system, like DegP and SurA, FkpA interacted with the unfolded EspP passenger domain ( Fig.…”

“…FkpA has also shown involvement in the autotransporter IgA protease secretion. 30 FkpA is a heatshock periplasmic peptidyl-prolyl cis/trans isomerase (PPIase) with chaperone activity 20,31 and its expression is activated via the σ E pathway. 32 Overexpression of FkpA epithelial cells.…”

“…15 Recently 16 On the other hand, the periplasmic proteins implicated in the targeting and assembly of extracytoplasmic proteins have shown three biological functions: molecular chaperones such as DegP, SurA, Skp and FkpA, [17][18][19][20] which stabilize non-native conformations of target proteins and facilitate their folding; peptidy prolyl cis-trans isomerases, such as SurA, PpiD and FkpA, [21][22][23] which catalyze the rate-limiting steps of isomerization during folding; and proteases, such as DegP and DegQ, 24 which degrade unproductive or misfolded proteins.…”

A rapid protein folding assay for the bacterial periplasm

“…22 It has been shown that the periplasmic chaperone FkpA can decrease aggregation of MalE31, whereas another periplasmic chaperone SurA did not affect MalE31 aggregation. 46 In addition, a periplasmic chaperone called Skp is well known for its ability to interact with a broad range of substrates 47 and has been used to improve expression of phagedisplayed proteins. 48 On the basis of these data, we reasoned that a chaperone-mediated decrease in MalE31 aggregation would lead to increased Bla activity in our assay.…”