Identification of Autotransporter Proteins Secreted by Type V Secretion Systems in Gram-Negative Bacteria

Autotransport in Gram-negative bacteria denotes the ability of surface-localized proteins to cross the outer membrane (OM) autonomously. Autotransporters perform this task with the help of a β-barrel transmembrane domain localized in the OM. Different classes of autotransporters have been investigated in detail in recent years; classical monomeric but also trimeric autotransporters comprise many important bacterial virulence factors. So do the two-partner secretion systems, which are a special case as the transported protein resides on a different polypeptide chain than the transporter. Despite the great interest in these proteins, the exact mechanism of the transport process remains elusive. Moreover, different periplasmic and OM factors have been identified that play a role in the translocation, making the term ‘autotransport’ debatable. In this review, we compile the wealth of details known on the mechanism of single autotransporters from different classes and organisms, and put them into a bigger perspective. We also discuss recently discovered or rediscovered classes of autotransporters.

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Structural comparison of the transport units of type V secretion systems

Biological Chemistry ◽

10.1515/hsz-2013-0162 ◽

2013 ◽

Vol 394 (11) ◽

pp. 1385-1398 ◽

Cited By ~ 8

Author(s):

Iris Gawarzewski ◽

Sander H.J. Smits ◽

Lutz Schmitt ◽

Joachim Jose

Keyword(s):

Outer Membrane ◽

Crystal Structure Analysis ◽

Type I ◽

Gram Negative Bacteria ◽

Secretion Systems ◽

X Ray ◽

Outer Membranes ◽

One Step ◽

Type V Secretion ◽

Type V

Abstract Pathogenic gram-negative bacteria have evolved several secretion mechanisms to translocate adhesins, enzymes, toxins, and other virulence factors across the inner and outer membranes. Currently, eight different secretion systems, type I–type VIII (T1SS–T8SS) plus the chaperone-usher (CU) pathway, have been identified, which act in one-step or two-step mechanisms to traverse both membrane barriers. The type V secretion system (T5SS) is dependent first on the Sec translocon within the inner membrane. The periplasmic intermediates are then secreted through aqueous pores formed by β-barrels in the outer membrane. Until now, transport across the outer membrane has not been understood on a molecular level. With respect to special characteristics revealed by crystal structure analysis, bioinformatic and biochemical data, five subgroups of T5SS were defined. Here, we compare the transport moieties of members of four subgroups based on X-ray crystal structures. For the fifth subgroup, which was identified only recently, no structures have thus far been reported. We also discuss different models for the translocation process across the outer membrane with respect to recent findings.

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Clonal Clusters, Molecular Resistance Mechanisms and Virulence Factors of Gram-Negative Bacteria Isolated from Chronic Wounds in Ghana

Antibiotics ◽

10.3390/antibiotics10030339 ◽

2021 ◽

Vol 10 (3) ◽

pp. 339

Author(s):

Denise Dekker ◽

Frederik Pankok ◽

Thorsten Thye ◽

Stefan Taudien ◽

Kwabena Oppong ◽

...

Keyword(s):

Molecular Epidemiology ◽

Virulence Factors ◽

Iron Uptake ◽

Chronic Wounds ◽

Sub Saharan Africa ◽

Gram Negative Bacteria ◽

Beta Lactamase ◽

Secretion Systems ◽

Gram Negative ◽

E Coli

Wound infections are common medical problems in sub-Saharan Africa but data on the molecular epidemiology are rare. Within this study we assessed the clonal lineages, resistance genes and virulence factors of Gram-negative bacteria isolated from Ghanaian patients with chronic wounds. From a previous study, 49 Pseudomonas aeruginosa, 21 Klebsiellapneumoniae complex members and 12 Escherichia coli were subjected to whole genome sequencing. Sequence analysis indicated high clonal diversity with only nine P. aeruginosa clusters comprising two strains each and one E. coli cluster comprising three strains with high phylogenetic relationship suggesting nosocomial transmission. Acquired beta-lactamase genes were observed in some isolates next to a broad spectrum of additional genetic resistance determinants. Phenotypical expression of extended-spectrum beta-lactamase activity in the Enterobacterales was associated with blaCTX-M-15 genes, which are frequent in Ghana. Frequently recorded virulence genes comprised genes related to invasion and iron-uptake in E. coli, genes related to adherence, iron-uptake, secretion systems and antiphagocytosis in P. aeruginosa and genes related to adherence, biofilm formation, immune evasion, iron-uptake and secretion systems in K. pneumonia complex. In summary, the study provides a piece in the puzzle of the molecular epidemiology of Gram-negative bacteria in chronic wounds in rural Ghana.

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Folding Control in the Path of Type 5 Secretion

Toxins ◽

10.3390/toxins13050341 ◽

2021 ◽

Vol 13 (5) ◽

pp. 341

Author(s):

Nathalie Dautin

Keyword(s):

Protein Folding ◽

Virulence Factors ◽

Secretion System ◽

Gram Negative Bacteria ◽

Secretion Systems ◽

Gram Negative ◽

Final Destination ◽

Cell Compartments ◽

Recent Addition ◽

Functionally Diverse

The type 5 secretion system (T5SS) is one of the more widespread secretion systems in Gram-negative bacteria. Proteins secreted by the T5SS are functionally diverse (toxins, adhesins, enzymes) and include numerous virulence factors. Mechanistically, the T5SS has long been considered the simplest of secretion systems, due to the paucity of proteins required for its functioning. Still, despite more than two decades of study, the exact process by which T5SS substrates attain their final destination and correct conformation is not totally deciphered. Moreover, the recent addition of new sub-families to the T5SS raises additional questions about this secretion mechanism. Central to the understanding of type 5 secretion is the question of protein folding, which needs to be carefully controlled in each of the bacterial cell compartments these proteins cross. Here, the biogenesis of proteins secreted by the Type 5 secretion system is discussed, with a focus on the various factors preventing or promoting protein folding during biogenesis.

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BastionHub: a universal platform for integrating and analyzing substrates secreted by Gram-negative bacteria

Nucleic Acids Research ◽

10.1093/nar/gkaa899 ◽

2020 ◽

Vol 49 (D1) ◽

pp. D651-D659

Author(s):

Jiawei Wang ◽

Jiahui Li ◽

Yi Hou ◽

Wei Dai ◽

Ruopeng Xie ◽

...

Keyword(s):

Rapid Development ◽

Single Type ◽

Computational Techniques ◽

Type I ◽

Gram Negative Bacteria ◽

Bacterial Survival ◽

Secretion Systems ◽

Gram Negative ◽

Relationship Analysis ◽

Depth Analysis

Abstract Gram-negative bacteria utilize secretion systems to export substrates into their surrounding environment or directly into neighboring cells. These substrates are proteins that function to promote bacterial survival: by facilitating nutrient collection, disabling competitor species or, for pathogens, to disable host defenses. Following a rapid development of computational techniques, a growing number of substrates have been discovered and subsequently validated by wet lab experiments. To date, several online databases have been developed to catalogue these substrates but they have limited user options for in-depth analysis, and typically focus on a single type of secreted substrate. We therefore developed a universal platform, BastionHub, that incorporates extensive functional modules to facilitate substrate analysis and integrates the five major Gram-negative secreted substrate types (i.e. from types I–IV and VI secretion systems). To our knowledge, BastionHub is not only the most comprehensive online database available, it is also the first to incorporate substrates secreted by type I or type II secretion systems. By providing the most up-to-date details of secreted substrates and state-of-the-art prediction and visualized relationship analysis tools, BastionHub will be an important platform that can assist biologists in uncovering novel substrates and formulating new hypotheses. BastionHub is freely available at http://bastionhub.erc.monash.edu/.

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