Type II secretion system pilotin lipoprotein (PulS_OutS)
This family comprises lipoproteins from four gamma proteobacterial species: PulS protein of Klebsiella pneumoniae (P20440), the OutS protein of Erwinia chrysanthemi (Q01567) and Pectobacterium chrysanthemi, and the functionally uncharacterized E. coli protein EtpO. PulS and OutS have been shown to interact with and facilitate insertion of secretins into the outer membrane, suggesting a chaperone-like, or piloting function for members of this family. In the pilotin from this four-helix protein from enterohemorrhagic Escherichia coli, the straight helix alpha2, the curved helix alpha3 and the bent helix alpha4 surround the central N-terminal helix alpha1. These helices create a prominent groove, mainly formed by side chains of helices 1,2 and 3 suggesting this groove is important as a binding site.