Pilotin-secretin recognition in the type II secretion system of Klebsiella oxytoca

Institut de Biologie Structurale, Bacterial Pathogenesis Group, Université Grenoble I, 41 rue Jules Horowitz, 38027 Grenoble, France.
Molecular Microbiology (Impact Factor: 4.42). 11/2011; 82(6):1422-32. DOI: 10.1111/j.1365-2958.2011.07896.x
Source: PubMed


A crucial aspect of the functionality of bacterial type II secretion systems is the targeting and assembly of the outer membrane secretin. In the Klebsiella oxytoca type II secretion system, the lipoprotein PulS, a pilotin, targets secretin PulD monomers through the periplasm to the outer membrane. We present the crystal structure of PulS, an all-helical bundle that is structurally distinct from proteins with similar functions. Replacement of valine at position 42 in a charged groove of PulS abolished complex formation between a non-lipidated variant of PulS and a peptide corresponding to the unfolded region of PulD to which PulS binds (the S-domain), in vitro, as well as PulS function in vivo. Substitutions of other residues in the groove also diminished the interaction with the S-domain in vitro but exerted less marked effects in vivo. We propose that the interaction between PulS and the S-domain is maintained through a structural adaptation of the two proteins that could be influenced by cis factors such as the fatty acyl groups on PulS, as well as periplasmic trans-acting factors, which represents a possible paradigm for chaperone-target protein interactions.

Download full-text


Available from: Bruno Baron, Oct 13, 2014
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Secretins are channels that allow translocation of macromolecules across the outer membranes of Gram-negative bacteria. Virulence, natural competence, and motility are among the functions mediated by these large oligomeric protein assemblies. Filamentous phage also uses secretins to exit their bacterial host without causing cell lysis. However, the secretin is only a part of a larger membrane-spanning complex, and additional proteins are often required for its formation. A class of outer membrane lipoproteins called pilotins has been implicated in secretin assembly and/or localization. Additional accessory proteins may also be involved in secretin stability. Significant progress has recently been made toward deciphering the complex interactions required for functional secretin assembly. To allow for easier comparison between different systems, we have classified the secretins into five different classes based on their requirements for proteins involved in their assembly, localization, and stability. An overview of pilotin and accessory protein structures, functions, and characterized modes of interaction with the secretin is presented.
    FEMS Microbiology Letters 11/2011; 328(1):1-12. DOI:10.1111/j.1574-6968.2011.02464.x · 2.12 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Many gram-negative bacteria use the sophisticated type II secretion system (T2SS) to translocate a wide range of proteins from the periplasm across the outer membrane. The inner-membrane platform of the T2SS is the nexus of the system and orchestrates the secretion process through its interactions with the periplasmic filamentous pseudopilus, the dodecameric outer-membrane complex and a cytoplasmic secretion ATPase. Here, recent structural and biochemical information is reviewed to describe our current knowledge of the biogenesis and architecture of the T2SS and its mechanism of action.
    Nature Reviews Microbiology 04/2012; 10(5):336-51. DOI:10.1038/nrmicro2762 · 23.57 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Secretins form large multimeric complexes in the outer membranes of many Gram-negative bacteria, where they function as dedicated gateways that allow proteins to access the extracellular environment. Despite their overall relatedness, different secretins use different specific and general mechanisms for their targeting, assembly, and membrane insertion. We report that all tested secretins from several type II secretion systems and from the filamentous bacteriophage f1 can spontaneously multimerize and insert into liposomes in an in vitro transcription-translation system. Phylogenetic analyses indicate that these secretins form a group distinct from the secretins of the type IV piliation and type III secretion systems, which do not autoassemble in vitro. A mutation causing a proline-to-leucine substitution allowed PilQ secretins from two different type IV piliation systems to assemble in vitro, albeit with very low efficiency, suggesting that autoassembly is an inherent property of all secretins.
    Journal of bacteriology 07/2012; 194(18):4951-8. DOI:10.1128/JB.00798-12 · 2.81 Impact Factor
Show more