Hydrophobic residues of the autotransporter EspP linker domain are important for outer membrane translocation of its passenger.
The autotransporter family of proteins is an important class of Gram-negative secreted virulence factors. Their secretion mechanism comprises entry to the periplasm via the Sec apparatus, followed by formation of an outer membrane beta barrel, which allows the N-terminal passenger domain to pass to the extracellular space. Several groups have identified a region immediately upstream of the beta domain that is important for outer membrane translocation, the so-called linker region. Here we characterize this region in EspP, a prototype of the serine protease autotransporters of enterobacteriaceae. We hypothesized that the folding of this region would be important in the outer membrane translocation process. We tested this hypothesis using a mutagenesis approach in conjunction with a series of nested deletions and found that in the absence of a complete passenger, mutations to the C-terminal helix, but not the upstream linker, significantly decrease secretion efficiency. However, in the presence of the passenger mutations to the amino-terminal region of the linker decrease secretion efficiency. Moreover, amino acids of hydrophobic character play a crucial role in linker function, suggesting the existence of a hydrophobic core or hydrophobic interaction necessary for outer membrane translocation of autotransporter proteins.
Velarde
Jorge J
JJ
Center for Vaccine Development, Department of Biochemistry, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
Nataro
James P
JP
D000595:Amino Acid Sequence; D001693:Biological Transport, Active; D017124:Conserved Sequence; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D057927:Hydrophobic and Hydrophilic Interactions; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
D029968:Escherichia coli Proteins; C107189:EspP protein, E coli; D012697:Serine Endopeptidases