Mycobacterium tuberculosis SatS is a chaperone for the SecA2 protein export pathway
- University of North Carolina at Chapel Hill, United States
- Texas A&M University, United States
Abstract
The SecA2 protein export system is critical for the virulence of Mycobacterium tuberculosis. However, the mechanism of this export pathway remains unclear. Through a screen for suppressors of a secA2 mutant, we identified a new player in the mycobacterial SecA2 pathway that we named SatS for SecA2 (two) Suppressor. In M. tuberculosis, SatS is required for the export of a subset of SecA2 substrates and for growth in macrophages. We further identify a role for SatS as a protein export chaperone. SatS exhibits multiple properties of a chaperone, including the ability to bind to and protect substrates from aggregation. Our structural studies of SatS reveal a distinct combination of a new fold and hydrophobic grooves resembling preprotein-binding sites of the SecB chaperone. These results are significant in better defining a molecular pathway for M. tuberculosis pathogenesis and in expanding our appreciation of the diversity among chaperones and protein export systems.
Data availability
All data generated and analysed during this study are included in the manuscript and supporting files. Figure supplements have been provided for Figures 1, 2, 5, and 8. Two additional supplementary tables describe the primers and plasmids used in this study. SatS C domain X-ray structure validation details are described in Figure 8-figure supplement 1 and have been deposited in PDB under the accession codes 6DRQ and 6DNM.
-
The crystal structure of SatS c-terminal domainProtein Data Bank, 6DNM.
-
Crystal Structure of SecB from Escherichia coliProtein Data Bank, 1QYN.
Article and author information
Author details
Funding
National Institute of Allergy and Infectious Diseases (AI054540)
- Brittany K Miller
- Lauren S Ligon
- Nathan W Rigel
- Seidu Malik
- Miriam Braunstein
National Institute of Allergy and Infectious Diseases (A-0015)
- Ryan Hughes
- James C Sacchettini
Welch Foundation (A-0015)
- Ryan Hughes
- James C Sacchettini
University of North Carolina (Graduate School Disseration Award)
- Brittany K Miller
National Institute of General Medical Sciences (GM055336)
- Brandon R Anjuwon-Foster
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Ethics
Animal experimentation: All animal care and experimental protocols were in strict accordance with the NIH Guide for the Care and Use of Laboratory Animals and were approved by the Institutional Animal Care and Use Committee of the University of North Carolina (protocol number 15-018.0).
Copyright
© 2019, Miller et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
Metrics
-
- 2,180
- views
-
- 356
- downloads
-
- 14
- citations
Views, downloads and citations are aggregated across all versions of this paper published by eLife.
Download links
A two-part list of links to download the article, or parts of the article, in various formats.
Downloads (link to download the article as PDF)
Open citations (links to open the citations from this article in various online reference manager services)
Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)
Mycobacterium tuberculosis SatS is a chaperone for the SecA2 protein export pathway
eLife 8:e40063.
https://doi.org/10.7554/eLife.40063
Further reading
-
- Microbiology and Infectious Disease
Saprolegnia parasitica is one of the most virulent oomycete species in freshwater aquatic environments, causing severe saprolegniasis and leading to significant economic losses in the aquaculture industry. Thus far, the prevention and control of saprolegniasis face a shortage of medications. Linalool, a natural antibiotic alternative found in various essential oils, exhibits promising antimicrobial activity against a wide range of pathogens. In this study, the specific role of linalool in protecting S. parasitica infection at both in vitro and in vivo levels was investigated. Linalool showed multifaceted anti-oomycetes potential by both of antimicrobial efficacy and immunomodulatory efficacy. For in vitro test, linalool exhibited strong anti-oomycetes activity and mode of action included: (1) Linalool disrupted the cell membrane of the mycelium, causing the intracellular components leak out; (2) Linalool prohibited ribosome function, thereby inhibiting protein synthesis and ultimately affecting mycelium growth. Surprisingly, meanwhile we found the potential immune protective mechanism of linalool in the in vivo test: (1) Linalool enhanced the complement and coagulation system which in turn activated host immune defense and lysate S. parasitica cells; (2) Linalool promoted wound healing, tissue repair, and phagocytosis to cope with S. parasitica infection; (3) Linalool positively modulated the immune response by increasing the abundance of beneficial Actinobacteriota; (4) Linalool stimulated the production of inflammatory cytokines and chemokines to lyse S. parasitica cells. In all, our findings showed that linalool possessed multifaceted anti-oomycetes potential which would be a promising natural antibiotic alternative to cope with S. parasitica infection in the aquaculture industry.
-
- Genetics and Genomics
- Microbiology and Infectious Disease
Polyamines are biologically ubiquitous cations that bind to nucleic acids, ribosomes, and phospholipids and, thereby, modulate numerous processes, including surface motility in Escherichia coli. We characterized the metabolic pathways that contribute to polyamine-dependent control of surface motility in the commonly used strain W3110 and the transcriptome of a mutant lacking a putrescine synthetic pathway that was required for surface motility. Genetic analysis showed that surface motility required type 1 pili, the simultaneous presence of two independent putrescine anabolic pathways, and modulation by putrescine transport and catabolism. An immunological assay for FimA—the major pili subunit, reverse transcription quantitative PCR of fimA, and transmission electron microscopy confirmed that pili synthesis required putrescine. Comparative RNAseq analysis of a wild type and ΔspeB mutant which exhibits impaired pili synthesis showed that the latter had fewer transcripts for pili structural genes and for fimB which codes for the phase variation recombinase that orients the fim operon promoter in the ON phase, although loss of speB did not affect the promoter orientation. Results from the RNAseq analysis also suggested (a) changes in transcripts for several transcription factor genes that affect fim operon expression, (b) compensatory mechanisms for low putrescine which implies a putrescine homeostatic network, and (c) decreased transcripts of genes for oxidative energy metabolism and iron transport which a previous genetic analysis suggests may be sufficient to account for the pili defect in putrescine synthesis mutants. We conclude that pili synthesis requires putrescine and putrescine concentration is controlled by a complex homeostatic network that includes the genes of oxidative energy metabolism.
