Protein secretion in gram-negative bacteria: transport across the outer membrane involves common mechanisms in different bacteria.

Abstract

The xcp genes are required for protein secretion by Pseudomonas aeruginosa. They are involved in the second step of the process, i.e. the translocation across the outer membrane, after the exoproteins have reached the periplasm in a signal peptide dependent fashion. The nucleotide sequence of a 2.5 kb DNA fragment containing xcp genes showed at least two complete open reading frames, potentially encoding proteins with molecular weights of 41 and 19 kd. Products with these apparent molecular weights were identified after expression of the DNA fragment in vitro and in vivo. Subcloning and complementation experiments showed that both proteins are required for secretion. The two products are located in the inner membrane and share highly significant homologies with the PulL and PulM proteins which are required for the specific secretion of pullulanase in Klebsiella pneumoniae. These homologies reveal the existence of a common mechanism for protein secretion in Pseudomonas aeruginosa and Klebsiella pneumoniae.

Extracellular secretion of pectate lyase by the Erwinia chrysanthemi out pathway is dependent upon Sec-mediated export across the inner membrane

“…The observation of related secretion processes among different gram-negative bacteria is consistent with the recent finding of similarity among the secretory genes of E. chrysanthemi (16), K. pneumoniae (42), P. aeruginosa (14), and E. carotovora subsp. carotovora (46a).…”

“…Secreted proteins of this group possess amino-terminal signal peptides which apparently function in E. coli in facilitating translocation of the proteins across the bacterial inner membrane (2,7,15,27,40,41,45). Extracellular secretion of these proteins, however, requires the function of accessory secretion genes, such as the out genes of E. chrysanthemi and Erwinia carotovora (1,26,37,50), the xcp genes of Pseudomonas aerguinosa (14), and the pul genes of K. pneumoniae (12). Recent reports of homology between the out, xcp, and pul genes suggest that gram-negative bacteria use a conserved mechanism to secrete proteins by this pathway (14,16).…”

Common components in the assembly of type 4 fimbriae, DNA transfer systems, filamentous phage and protein‐secretion apparatus: a general system for the formation of surface‐associated protein complexes

“…These include Erwinia species (secretion of enzymes which degrade the plant cell wall) (He et al, 1991;~ondemine et al, 1992;Lindeberg and eollmer, 1992;Reeves et al, 1993), Xanthomonas campestris (secretion of a range of extracellular enzymes, including pectate Iyases and cellulases) (Dums et al, 1991, Hu et al, 1992, and the opportunistic animal pathogens Aeromonas hydrophila (secretion of the toxin aerolysin and other proteins) (Jiang and Howard , 1992) and P. aeruginosa (secretion of numerous proteins, including elastase, alkaline phosphatase, phospholipase e, and exotoxin A) (Lazdunski et al, 1990;Bally et al, 1991 ;Filloux et al, 1991 ;Nunn and Lory, 1992;Tommassen et al, 1992: Akrim et aI., 1993. Recently it has been shown (Sandkvist et al, 1993) that secretion of cholera toxin by V. cholerae requires a gene, epsE, which is a homologue of pulE (Martin et al, 1993).…”

Regulation of the xcp secretion pathway by multiple quorum‐sensing modulons in Pseudomonas aeruginosa

“…However, genetic analysis of the xcp cluster located at 40 min on the chromosome of P. aeruginosa revealed a different genetic organization. Nine xcp genes, xcpR to xcpZ, are arranged in a single operon structure, whereas xcpP and xcpQ are co-transcribed divergently with respect to the xcpR to xcpZ operon (Akrim et al, 1993;Bally et al, 1992;Filloux et al, 1990).…”