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Muthuramalingam M, Whittier SK, Lovell S, Battaile KP, Tachiyama S, Johnson DK, Picking WL, Picking WD. The Structures of SctK and SctD from Pseudomonas aeruginosa Reveal the Interface of the Type III Secretion System Basal Body and Sorting Platform. J Mol Biol 2020; 432:166693. [PMID: 33122003 PMCID: PMC10550303 DOI: 10.1016/j.jmb.2020.10.027] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Revised: 10/20/2020] [Accepted: 10/21/2020] [Indexed: 10/23/2022]
Abstract
Many Gram-negative bacterial pathogens use type III secretion systems (T3SS) to inject proteins into eukaryotic cells to subvert normal cellular functions. The T3SS apparatus (injectisome) shares a common architecture in all systems studied thus far, comprising three major components - the cytoplasmic sorting platform, envelope-spanning basal body and external needle with tip complex. The sorting platform consists of an ATPase (SctN) connected to "pods" (SctQ) having six-fold symmetry via radial spokes (SctL). These pods interface with the 24-fold symmetric SctD inner membrane ring (IR) via an adaptor protein (SctK). Here we report the first high-resolution structure of a SctK protein family member, PscK from Pseudomonas aeruginosa, as well as the structure of its interacting partner, the cytoplasmic domain of PscD (SctD). The cytoplasmic domain of PscD forms a forkhead-associated (FHA) fold, like that of its homologues from other T3SS. PscK, on the other hand, forms a helix-rich structure that does not resemble any known protein fold. Based on these structural findings, we present the first model for an interaction between proteins from the sorting platform and the IR. We also test the importance of the PscD residues predicted to mediate this electrostatic interaction using a two-hybrid analysis. The functional need for these residues in vivo was then confirmed by monitoring secretion of the effector ExoU. These structures will contribute to the development of atomic-resolution models of the entire sorting platform and to our understanding of the mechanistic interface between the sorting platform and the basal body of the injectisome.
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Affiliation(s)
| | - Sean K Whittier
- Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, KS 66047, United States
| | - Scott Lovell
- Protein Structure Laboratory, Del Shankel Structural Biology Center, University of Kansas, Lawrence, KS 66047, United States
| | - Kevin P Battaile
- IMCA-CAT, Hauptman Woodward Medical Research Institute, Argonne, IL 60439, United States
| | - Shoichi Tachiyama
- Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, KS 66047, United States
| | - David K Johnson
- Computational Chemical Biology Laboratory, Del Shankel Structural Biology Center, University of Kansas, Lawrence, KS 66047, United States
| | - Wendy L Picking
- Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, KS 66047, United States
| | - William D Picking
- Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, KS 66047, United States.
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Cheng WH, Huang KY, Huang PJ, Lee CC, Yeh YM, Ku FM, Lin R, Cheng ML, Chiu CH, Tang P. γ-Carboxymuconolactone decarboxylase: a novel cell cycle-related basal body protein in the early branching eukaryote Trichomonas vaginalis. Parasit Vectors 2017; 10:443. [PMID: 28950916 PMCID: PMC5615479 DOI: 10.1186/s13071-017-2381-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Accepted: 09/14/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND γ-Carboxymuconolactone decarboxylase (CMD) participates in the β-ketoadipate pathway, which catalyzes aromatic compounds to produce acetyl- or succinyl-CoA, in prokaryotes and yeast. Our previous study demonstrated that expression of a CMD homologue that contains two signatures (dualCMD) is negatively regulated by iron in Trichomonas vaginalis. However, we were not able to identify the components of the β-ketoadipate pathway in the parasite's genome. These observations prompted us to investigate the biological functions of this novel CMD homologue in T. vaginalis. METHODS The specific anti-TvCMD1 antibody was generated, and the expression of TvCMD1 in T. vaginalis cultured under iron-rich and iron-deficient were evaluated. Phylogenetic, metabolomic and substrate induction (protocatechuate and benzoate) analysis were conducted to clarify the function of dualCMD in trichomonad cells. Subcellular localization of TvCMD1 was observed by confocal microscopy. The cell cycle-related role of TvCMD1 was assessed by treating cells with G2/M inhibitor nocodazole. RESULTS We confirmed that T. vaginalis is not able to catabolize the aromatic compounds benzoate and protocatechuate, which are known substrates of the β-ketoadipate pathway. Using immunofluorescence microscopy, we found that TvCMD1 is spatially associated with the basal body, a part of the cytoskeletal organizing center in T. vaginalis. TvCMD1 accumulated upon treatment with the G2/M inhibitor nocodazole. Additionally, TvCMD1 was expressed and transported to/from the basal body during cytokinesis, suggesting that TvCMD1 plays a role in cell division. CONCLUSION We demonstrated that TvCMD1 is unlikely to participate in the β-ketoadipate pathway and demonstrated that it is a novel basal body-localizing (associated) protein. This model sheds light on the importance of genes that are acquired laterally in the coevolution of ancient protists, which surprisingly functions in cell cycle regulation of T. vaginalis.
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Affiliation(s)
- Wei-Hung Cheng
- Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Kweishan, Taoyuan, Taiwan
- Molecular Regulation and Bioinformatics Laboratory, Department of Parasitology, College of Medicine, Chang Gung University, Kweishan, Taoyuan, Taiwan
| | - Kuo-Yang Huang
- Graduate Institute of Pathology and Parasitology, National Defense Medical Center, Taipei, Taiwan
| | - Po-Jung Huang
- Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Kweishan, Taoyuan, Taiwan
- Bioinformatics Core Laboratory, Molecular Medicine Research Center, Chang Gung University, Kweishan, Taoyuan, Taiwan
- Department of Biomedical Sciences, College of Medicine, Chang Gung University, Kweishan, Taoyuan, Taiwan
| | - Chi-Ching Lee
- Department and Graduate Institute of Computer Science and Information Engineering, College of Engineering, Chang Gung University, Kweishan, Taoyuan, Taiwan
| | - Yuan-Ming Yeh
- Bioinformatics Core Laboratory, Molecular Medicine Research Center, Chang Gung University, Kweishan, Taoyuan, Taiwan
| | - Fu-Man Ku
- Molecular Regulation and Bioinformatics Laboratory, Department of Parasitology, College of Medicine, Chang Gung University, Kweishan, Taoyuan, Taiwan
| | - Rose Lin
- Molecular Regulation and Bioinformatics Laboratory, Department of Parasitology, College of Medicine, Chang Gung University, Kweishan, Taoyuan, Taiwan
| | - Mei-Ling Cheng
- Department of Biomedical Sciences, College of Medicine, Chang Gung University, Kweishan, Taoyuan, Taiwan
| | - Cheng-Hsun Chiu
- Molecular Infectious Disease Research Center, Chang Gung Memorial Hospital, Kweishan, Taoyuan, Taiwan
| | - Petrus Tang
- Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Kweishan, Taoyuan, Taiwan
- Molecular Regulation and Bioinformatics Laboratory, Department of Parasitology, College of Medicine, Chang Gung University, Kweishan, Taoyuan, Taiwan
- Bioinformatics Core Laboratory, Molecular Medicine Research Center, Chang Gung University, Kweishan, Taoyuan, Taiwan
- Molecular Infectious Disease Research Center, Chang Gung Memorial Hospital, Kweishan, Taoyuan, Taiwan
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