Glycine‐144 is required for efficient folding of outer membrane protein PhoE of Escherichia coli K12

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Abstract
Short stretches of similar sequences have been detected in unrelated bacterial outer membrane proteins (Nikaido and Wu (1984) Proc. Natl. Acad. Sci. USA 81, 1048-1052). In the most pronounced similarity region, only a glycine residue is absolutely conserved. To investigate whether this glycine residue is essential for outer membrane incorporation, oligonucleotide-directed mutagenesis was applied to replace this residue, i.e. Gly-144, as well as two other Gly-residues in pore protein PhoE. Substitution of Gly-52 and Gly-258 by Ala And Val, respectively, did not influence outer membrane incorporation. However, the substitution of Gly-144 by Leu affected the efficiency of outer membrane incorporation. After in vitro synthesis this mutant protein was less efficiency precipitated with monoclonal antibodies that recognize coformational epitopes than wild-type PhoE, showing that the mutation interferes with correct folding of the protein