Table 1.

Summary of selected in vitro folding studies of outer membrane proteins (OMPs) into lipid bilayers.

Protein	Notes	Techniques used	Selected References
OmpA	Folding studies of OmpA are described in this review and elsewhere.	Cold SDS–PAGE, far-UV CD, Trp fluorescence	Kleinschmidt (2006) [171]; Otzen (2013) [58]
PagP	Folding studies of a C-terminally his-tagged construct of PagP (HT PagP) and untagged construct (PagP) are described in detail in this review.	Cold SDS–PAGE, far-UV CD, Trp fluorescence, Φ-value analysis	Bishop et al. (2000) [239]; Ahn et al. (2004) [206]; Huysmans et al. (2010) [157]
hVDAC	Human voltage-dependent anion-selective channel (hVDAC) can be folded to the native state in LUVs composed of lipids of varying acyl chain length (diC10:0PC to diC18:1PC). Folding yield was estimated to be 94% in diC12:0PC LUVs. Secondary structure content of hVDAC in diC12:0PC LUVs was not affected by changing pH from 7.0 to 3.0.	Cold SDS–PAGE, far-UV CD, Trp fluorescence, sucrose density gradient centrifugation and proteolysis	Shanmugavadivu et al. (2007) [225]
FomA	FomA can be folded to the native state in both diC10:0PC and diC18:1PC (LUVs and SUVs). Kinetic analysis of folding into diC10:0PC and diC18:1PC SUVs suggested that FomA folds via parallel pathways into both lipids. The folding halftime is dependent on acyl chain length and reaction temperature.	Cold SDS–PAGE, Trp fluorescence, far-UV CD	Pocanschi et al. (2006) [202]
OmpG	The porin OmpG reconstituted in native E. coli lipids is gated by conformational changes in extracellular loops in a pH-dependent manner (closed at pH 5.0). Unfolding under force reveals each β-hairpin unfolds individually. Refolding from this mechanically unfolded state also proceeds by sequential folding of individual β-hairpins.	Atomic force microscopy (AFM)	Sapra et al. (2009) [240]; Damaghi et al. (2010) [241]; Mari et al. (2010) [242]; Damaghi et al. (2011) [243]
OmpF	Refolding of urea-solubilised OmpF into diC14:0PC SUVs occurred at only 15% yield. Refolding kinetics were biphasic but much slower than OmpA.	Cold SDS–PAGE, Trp fluorescence, far-UV CD	Surrey et al. (1996) [244]