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Lo SY, Goulet DL, Fraaz U, Siemann S. Effect of pH and denaturants on the fold and metal status of anthrax lethal factor. Arch Biochem Biophys 2020; 692:108547. [PMID: 32828796 DOI: 10.1016/j.abb.2020.108547] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 08/02/2020] [Accepted: 08/17/2020] [Indexed: 01/26/2023]
Abstract
Anthrax lethal factor (LF) is a critical component of the anthrax toxin, and functions intracellularly as a zinc-dependent endopeptidase targeting proteins involved in maintaining critical host signaling pathways. To reach the cytoplasm, LF requires to be unfolded and guided through the narrow protective antigen pore in a pH-dependent process. The current study sought to address the question as to whether LF is capable of retaining its metal ion when exposed to a low-pH environment (similar to that found in late endosomes) and an unfolding stress (induced by urea). Using a combination of tryptophan fluorescence spectroscopy and chelation studies, we show that a decrease in the pH value (from 7.0 to 5.0) leads to a pronounced shift in the onset of structural alterations in LF to lower urea concentrations. More importantly, the enzyme was found to retain its Zn2+ ion beyond the unfolding transitions monitored by Trp fluorescence, a finding indicative of tight metal binding to LF in a non-native state. In addition, an analysis of red-edge excitation shift (REES) spectra suggests the protein to maintain residual structure (a feature necessary for metal binding) even at very high denaturant concentrations. Furthermore, studies using the chromophoric chelator 4-(2-pyridylazo)resorcinol (PAR) revealed LF's Zn2+ ion to become accessible to complexation at urea concentrations in between those required to cause structural changes and metal dissociation. This phenomenon likely originates from the conversion of a PAR-inaccessible (closed) to a PAR-accessible (open) state of LF at intermediate denaturant concentrations.
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Affiliation(s)
- Suet Y Lo
- Department of Chemistry and Biochemistry, Laurentian University, Sudbury, Ontario, P3E 2C6, Canada
| | - Danica L Goulet
- Department of Chemistry and Biochemistry, Laurentian University, Sudbury, Ontario, P3E 2C6, Canada
| | - Usama Fraaz
- Department of Chemistry and Biochemistry, Laurentian University, Sudbury, Ontario, P3E 2C6, Canada
| | - Stefan Siemann
- Department of Chemistry and Biochemistry, Laurentian University, Sudbury, Ontario, P3E 2C6, Canada.
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Walker MA, Uribasterra M, Asher V, Ponciano JM, Getz WM, Ryan SJ, Blackburn JK. Ungulate use of locally infectious zones in a re-emerging anthrax risk area. ROYAL SOCIETY OPEN SCIENCE 2020; 7:200246. [PMID: 33204443 PMCID: PMC7657905 DOI: 10.1098/rsos.200246] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Accepted: 09/18/2020] [Indexed: 05/05/2023]
Abstract
Environmentally mediated indirect pathogen transmission is linked to host movement and foraging in areas where pathogens are maintained in the environment. In the case of anthrax, spores of the causative bacterium Bacillus anthracis are released into the environment following host death and create locally infectious zones (LIZs) around carcass sites; by grazing at LIZs, herbivores are potentially exposed to spores. Here, we used camera traps to assess how ungulate species use carcass sites in southwestern Montana and evaluated how these behaviours may promote indirect anthrax transmission, thus providing, to our knowledge, the first detailed documentation and study of the fine-scale mechanisms underlying foraging-based disease transmission in this ecosystem. We found that carcasses at LIZs significantly increased aboveground biomass of vegetation and concentrations of sodium and phosphorus, potentially making these sites more appealing to grazers. Host behavioural responses to LIZs varied depending on species, sex, season and carcass age; but, overall, our results demonstrated that carcasses or carcass sites serve as an attractant to herbivores in this system. Attraction to LIZs probably represents an increased risk of exposure to B. anthracis and, consequently, increased anthrax transmission rates. Accordingly, continued anthrax surveillance and control strategies are critical in this system.
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Affiliation(s)
- Morgan A. Walker
- Spatial Epidemiology and Ecology Research Laboratory, University of Florida, Gainesville, FL, USA
- Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA
| | - Maria Uribasterra
- Spatial Epidemiology and Ecology Research Laboratory, University of Florida, Gainesville, FL, USA
- Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA
| | - Valpa Asher
- Turner Enterprises Inc., 1123 Research Drive, Bozeman, MT, USA
| | | | - Wayne M. Getz
- Department of Environmental Sciences, Policy, and Management, University of California, Berkeley, 130 Mulford Hall, Berkeley, CA, USA
- School of Mathematical Sciences, University of KwaZulu-Natal, Durban, South Africa
| | - Sadie J. Ryan
- Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA
- Quantitative Disease Ecology and Conservation Laboratory, Department of Geography, University of Florida, Gainesville, FL, USA
| | - Jason K. Blackburn
- Spatial Epidemiology and Ecology Research Laboratory, University of Florida, Gainesville, FL, USA
- Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA
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Yin X, Mu L, Wu H, Han K, Guo Z, Ye J. Expression and functional analysis of Nile tilapia transferrin receptors (TfRs) in host resistance to pathogenic bacteria and iron ion metabolism. FISH & SHELLFISH IMMUNOLOGY 2020; 100:407-417. [PMID: 32200071 DOI: 10.1016/j.fsi.2020.03.027] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Revised: 03/04/2020] [Accepted: 03/11/2020] [Indexed: 06/10/2023]
Abstract
Transferrin receptors (TfRs) play an essential role in iron-withholding strategy, and are involved in immune response against bacterial infection. In this study, the transferrin receptor 1 (OnTfR1) and transferrin receptor 2 (OnTfR2) genes are identified and characterized in Nile tilapia (Oreochromis niloticus). The open reading frames of OnTfR1 and OnTfR2 are 2220 and 2343 bp of nucleotide sequence, encoding 739 and 780 amino acids, respectively. The deduced proteins of OnTfR1 and OnTfR2 are highly homologous to those of other species, containing three conserved TfR superfamily domains (PA TfR domain, M28 TfR domain and TfR dimer domain). Expression analyses of OnTfRs in the healthy tilapia reveal that the OnTfR1 and OnTfR2 transcripts are the most abundant in the liver. The in vivo studies show that the expressions of OnTfRs are significantly up-regulate in liver and spleen, following infections of Streptococcus agalactiae and Aeromonas hydrophila. In addition, the in vitro studies reveal that the up-regulations of OnTfR expressions are also significant in monocytes/macrophages and hepatocytes upon the stimulations of S. agalactiae and A. hydrophila. Moreover, the iron ion (Fe3+) could significantly increase the expressions of OnTfRs in monocytes/macrophages and hepatocytes. Taken together, the present study indicates that OnTfRs may be involved in host defense against bacterial infection and possess the function of combining or transporting iron ions in Nile tilapia.
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Affiliation(s)
- Xiaoxue Yin
- Institute of Modern Aquaculture Science and Engineering, School of Life Sciences, South China Normal University, Guangdong Provincial Key Laboratory for Healthy and Safe Aquaculture, Guangdong Provincial Engineering Technology Research Center for Environmentally-Friendly Aquaculture, Guangzhou, 510631, PR China
| | - Liangliang Mu
- Institute of Modern Aquaculture Science and Engineering, School of Life Sciences, South China Normal University, Guangdong Provincial Key Laboratory for Healthy and Safe Aquaculture, Guangdong Provincial Engineering Technology Research Center for Environmentally-Friendly Aquaculture, Guangzhou, 510631, PR China
| | - Hairong Wu
- Institute of Modern Aquaculture Science and Engineering, School of Life Sciences, South China Normal University, Guangdong Provincial Key Laboratory for Healthy and Safe Aquaculture, Guangdong Provincial Engineering Technology Research Center for Environmentally-Friendly Aquaculture, Guangzhou, 510631, PR China
| | - Kailiang Han
- Institute of Modern Aquaculture Science and Engineering, School of Life Sciences, South China Normal University, Guangdong Provincial Key Laboratory for Healthy and Safe Aquaculture, Guangdong Provincial Engineering Technology Research Center for Environmentally-Friendly Aquaculture, Guangzhou, 510631, PR China
| | - Zheng Guo
- Institute of Modern Aquaculture Science and Engineering, School of Life Sciences, South China Normal University, Guangdong Provincial Key Laboratory for Healthy and Safe Aquaculture, Guangdong Provincial Engineering Technology Research Center for Environmentally-Friendly Aquaculture, Guangzhou, 510631, PR China
| | - Jianmin Ye
- Institute of Modern Aquaculture Science and Engineering, School of Life Sciences, South China Normal University, Guangdong Provincial Key Laboratory for Healthy and Safe Aquaculture, Guangdong Provincial Engineering Technology Research Center for Environmentally-Friendly Aquaculture, Guangzhou, 510631, PR China.
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