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Wu HP, Derilo RC, Chen HL, Li TR, Lagitnay RBJS, Chan YC, Chuang Y, Chuang DY. Injectisome T3SS subunits as potential chaperones in the extracellular export of Pectobacterium carotovorum subsp. carotovorum bacteriocins Carocin S1 and Carocin S3 secreted via flagellar T3SS. BMC Microbiol 2021; 21:345. [PMID: 34911446 PMCID: PMC8672553 DOI: 10.1186/s12866-021-02405-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Accepted: 11/26/2021] [Indexed: 12/27/2022] Open
Abstract
Pectobacterium carotovorum subsp. carotovorum (Pcc) causes soft-rot disease in a wide variety of plants resulting in economic losses worldwide. It produces various types of bacteriocin to compete against related plant pathogens. Studies on how bacteriocins are extracellularly secreted are conducted to understand the mechanism of interbacterial competition. In this study, the secretion of the low-molecular-weight bacteriocins (LMWB) Carocin S1 and Carocin S3 produced by a multiple-bacteriocin producing strain of Pcc, 89-H-4, was investigated. Tn5 insertional mutagenesis was used to generate a mutant, TH22–6, incapable of LMWBs secretion. Sequence and homology analyses of the gene disrupted by transposon Tn5 insertion revealed that the gene sctT, an essential component of the injectisome type III secretion machinery (T3aSS), is required for the secretion of the bacteriocins. This result raised a question regarding the nature of the secretion mechanism of Pcc bacteriocins which was previously discovered to be secreted via T3bSS, a system that utilizes the bacterial flagellum for extracellular secretions. Our previous report has shown that bacteriocin Carocin S1 cannot be secreted by mutants that are defective of T3bSS-related genes such as flhA, flhC, flhD and fliC. We knocked out several genes making up the significant structural components of both T3aSS and T3bSS. The findings led us to hypothesize the potential roles of the T3aSS-related proteins, SctT, SctU and SctV, as flagellar T3SS chaperones in the secretion of Pcc bacteriocins. This current discovery and the findings of our previous study helped us to conceptualize a unique Type III secretion system for bacteriocin extracellular export which is a hybrid of the injectisome and flagellar secretion systems.
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Affiliation(s)
- Huang-Pin Wu
- Division of Pulmonary, Critical Care and Sleep Medicine, Chang Gung Memorial Hospital, Keelung, Taiwan.,College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Reymund C Derilo
- Department of Chemistry, National Chung Hsing University, 145, Xingda Rd., Taichung, 402, Taiwan.,College of Teacher Education, Nueva Vizcaya State University Bambang Campus, Bambang, Nueva Vizcaya, Philippines
| | - Han-Ling Chen
- Department of Chemistry, National Chung Hsing University, 145, Xingda Rd., Taichung, 402, Taiwan
| | - Tzu-Rung Li
- Department of Chemistry, National Chung Hsing University, 145, Xingda Rd., Taichung, 402, Taiwan
| | - Ruchi Briam James S Lagitnay
- Department of Chemistry, National Chung Hsing University, 145, Xingda Rd., Taichung, 402, Taiwan.,College of Arts and Sciences, Nueva Vizcaya State University Bayombong Campus, Bayombong, Nueva Vizcaya, Philippines
| | - Yung-Chieh Chan
- Department of Chemistry, National Chung Hsing University, 145, Xingda Rd., Taichung, 402, Taiwan
| | - Yutin Chuang
- Department of Entomology, National Chung Hsing University, Taichung City, Taiwan
| | - Duen-Yau Chuang
- Department of Chemistry, National Chung Hsing University, 145, Xingda Rd., Taichung, 402, Taiwan.
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Khater L, Alegria MC, Borin PFL, Santos TM, Docena C, Tasic L, Farah CS, Ramos CHI. Identification of the flagellar chaperone FlgN in the phytopathogen Xanthomonas axonopodis pathovar citri by its interaction with hook-associated FlgK. Arch Microbiol 2007; 188:243-50. [PMID: 17492271 DOI: 10.1007/s00203-007-0240-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2007] [Revised: 03/06/2007] [Accepted: 03/24/2007] [Indexed: 01/30/2023]
Abstract
Genome annotation of the plant pathogen Xanthomonas axonopodis pv. citri (Xac), identified flagellar genes in a 15.7 kb gene cluster. However, FlgN, a secretion chaperone for hook-associated proteins FlgK and FlgL, was not identified. We performed extensive screening of the X. axonopodis pv. citri genome with the yeast two-hybrid system to identify a protein with the characteristics of the flagellar chaperone FlgN. We found a candidate (XAC1990) encoded by an operon for components of the flagellum apparatus that interacted with FlgK. In order to further support this finding, Xac FlgK and XAC1990 were cloned, expressed, and purified. The recombinant proteins were characterized by spectroscopic methods and their interaction in vitro confirmed by pull-down assays. We, therefore, conclude that XAC1990 and its homologs in other Xanthomonas species are, in fact, FlgN proteins. These observations extend the sequence diversity covered by this family of proteins.
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Affiliation(s)
- Letícia Khater
- Laboratório Nacional de Luz Síncrotron, CEP 13084-971 Campinas, SP, Brazil
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Tasic L, Borin PFL, Khater LC, Ramos CHI. Cloning and characterization of three hypothetical secretion chaperone proteins from Xanthomonas axonopodis pv. citri. Protein Expr Purif 2007; 53:363-9. [PMID: 17350859 DOI: 10.1016/j.pep.2007.01.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2006] [Revised: 01/19/2007] [Accepted: 01/24/2007] [Indexed: 11/17/2022]
Abstract
Xanthomonas axonopodis pv. citri (Xac) causes citrus canker in plantations around the world and is of particular significance in Brazil where its incidence has risen exponentially over the past decade. Approximately one third of the predicted Xac open reading frames show no homology, or homology with very low score with that of known sequences. It is believed that Xac utilizes secretion systems to transfer virulence proteins into susceptible eukaryotic cells. This process is assisted by secretion chaperones that maintain virulence proteins partly or completely unfolded during translocation. We have cloned three of these hypothetical secretion chaperones: XAC0419 and XAC1346 from type III secretion system (TTSS) and XACb0033 from type IV secretion system (TFSS). All proteins were cloned in a pET23a vector (Novagen), expressed at 37 degrees C using a BL21(DE3)pLysS Escherichia coli strain and purified by ion exchange and gel-filtration chromatographic methods. Pure proteins were characterized using spectroscopic measurements: circular dichroism, and both static and lifetime emission fluorescence in the case of XACb0033. The analyzed proteins are stable at elevated temperatures (up to 65 degrees C) and exhibit alpha-helix content from approximately 30% (XACb003) to approximately 87% (XAC1346). XACb0033 exhibits lifetimes in the fluorescence experiments that indicate different neighborhoods for its tryptophan residues. These chaperones have the characteristics of TTSS and TFSS: all are small, with a high alpha-helix content, and without ATP-binding or ATP-hydrolyzing activity.
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Affiliation(s)
- Ljubica Tasic
- Chemistry Institute, UNICAMP, P.O. Box 6154, Campinas, SP, Brazil.
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