Title: A Genomic Island of Vibrio cholerae Encodes a Three-Component Cytotoxin with Monomer and Protomer Forms Structurally Similar to Alpha-Pore-Forming Toxins

Abstract

Alpha-pore-forming toxins (α-PFTs) are secreted by many species of bacteria, including Escherichia coli, Aeromonas hydrophila, and Bacillus thuringiensis, as part of their arsenal of virulence factors, and are often cytotoxic. In particular, for α-PFTs, the membrane-spanning channel they form is composed of hydrophobic α-helices. These toxins oligomerize at the surface of target cells and transition from a soluble to a protomer state in which they expose their hydrophobic regions and insert into the membrane to form a pore. The pores may be composed of homooligomers of one component or heterooligomers with two or three components, resulting in bi- or tripartite toxins. The multicomponent α-PFTs are often expressed from a single operon. Recently, motility-associated killing factor A (MakA), an α-PFT, was discovered in Vibrio cholerae. We report that makA is found on the V. cholerae GI-10 genomic island within an operon containing genes for two other potential α-PFTs, MakB and MakE. We determined the X-ray crystal structures for MakA, MakB, and MakE and demonstrated that all three are structurally related to the α-PFT family in the soluble state, and we modeled their protomer state based on the α-PFT AhlB from A. hydrophila. We found that MakA alone is cytotoxic at micromolarmore » concentrations. However, combining MakA with MakB and MakE is cytotoxic at nanomolar concentrations, with specificity for J774 macrophage cells. Our data suggest that MakA, -B, and -E are α-PFTs that potentially act as a tripartite pore-forming toxin with specificity for phagocytic cells. The bacterium Vibrio cholerae causes gastrointestinal, wound, and skin infections. The motility-associated killing factor A (MakA) was recently shown to be cytotoxic against colon, prostate, and other cancer cells. However, at the outset of this study, the capacity of MakA to damage cells in combination with other Mak proteins encoded in the same operon had not been elucidated. We determined the structures of three Mak proteins and established that they are structurally related to the α-PFTs. Compared to MakA alone, the combination of all three toxins was more potent specifically in mouse macrophages. This study highlights the idea that the Mak toxins are selectively cytotoxic and thus may function as a tripartite toxin with cell type specificity.« less

Authors:

Herrera, Alfa ^[1]; Kim, Youngchang ^[2]; Chen, Jiexi ^[1]; Jedrzejczak, Robert ^[2]; Shukla, Shantanu ^[1]; Maltseva, Natalia ^[2]; Joachimiak, Grazyna ^[2]; Welk, Lukas ^[2]; Wiersum, Grant ^[1]; Jaroszewski, Lukasz ^[3]; Godzik, Adam ^[3]; Joachimiak, Andrzej ^[2]; Satchell, Karla F.  ^[1]

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+ Show Author Affiliations

1. Northwestern University, Chicago, IL (United States)
2. University of Chicago, IL (United States); Argonne National Laboratory (ANL), Lemont, IL (United States)
3. University of California, Riverside, CA (United States)

Publication Date:

Mon Apr 18 00:00:00 EDT 2022

Research Org.:

Argonne National Laboratory (ANL), Argonne, IL (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER); National Institute of Allergy and Infectious Diseases (NIAID); National Institutes of Health (NIH); Department of Health and Human Services

OSTI Identifier:

1909700

Grant/Contract Number:  

AC02-06CH11357; HHSN272201700060C; R01 AI092825-09; R01 AI092825-S1; K99 GM143571-01; T32 GM008382

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Bacteriology

Additional Journal Information:

Journal Volume: 204; Journal Issue: 5; Journal ID: ISSN 0021-9193

Publisher:

American Society for Microbiology

Country of Publication:

United States

Language:

English

Subject:

59 BASIC BIOLOGICAL SCIENCES; Vibrio cholerae; apoptosis; cell biology; cytotoxins; macrophages; pore-forming toxins; three-dimensional structure