1
|
Ye P, Li X, Cui B, Song S, Shen F, Chen X, Wang G, Zhou X, Deng Y. Proline utilization A controls bacterial pathogenicity by sensing its substrate and cofactors. Commun Biol 2022; 5:496. [PMID: 35614320 PMCID: PMC9132996 DOI: 10.1038/s42003-022-03451-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Accepted: 05/05/2022] [Indexed: 11/26/2022] Open
Abstract
Previous reports indicate that proline utilization A (PutA) is involved in the oxidation of proline to glutamate in many bacteria. We demonstrate here that in addition to its role in proline catabolism, PutA acts as a global regulator to control the important biological functions and virulence of Ralstonia solanacearum. PutA regulates target gene expression levels by directly binding to promoter DNA, and its regulatory activity is enhanced by L-proline. Intriguingly, we reveal that the cofactors NAD+ and FAD boost the enzymatic activity of PutA for converting L-proline to L-glutamic acid but inhibit the regulatory activity of PutA for controlling target gene expression. Our results present evidence that PutA is a proline metabolic enzyme that also functions as a global transcriptional regulator in response to its substrate and cofactors and provide insights into the complicated regulatory mechanism of PutA in bacterial physiology and pathogenicity.
Collapse
Affiliation(s)
- Peiyi Ye
- School of Pharmaceutical Sciences (Shenzhen), Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen, 518107, China
- Integrative Microbiology Research Center, College of Plant Protection, South China Agricultural University, Guangzhou, 510642, China
| | - Xia Li
- School of Pharmaceutical Sciences (Shenzhen), Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen, 518107, China
| | - Binbin Cui
- School of Pharmaceutical Sciences (Shenzhen), Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen, 518107, China
| | - Shihao Song
- School of Pharmaceutical Sciences (Shenzhen), Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen, 518107, China
- Integrative Microbiology Research Center, College of Plant Protection, South China Agricultural University, Guangzhou, 510642, China
| | - Fangfang Shen
- Integrative Microbiology Research Center, College of Plant Protection, South China Agricultural University, Guangzhou, 510642, China
| | - Xiayu Chen
- School of Pharmaceutical Sciences (Shenzhen), Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen, 518107, China
| | - Gerun Wang
- School of Pharmaceutical Sciences (Shenzhen), Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen, 518107, China
| | - Xiaofan Zhou
- Integrative Microbiology Research Center, College of Plant Protection, South China Agricultural University, Guangzhou, 510642, China
| | - Yinyue Deng
- School of Pharmaceutical Sciences (Shenzhen), Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen, 518107, China.
| |
Collapse
|
2
|
Christgen SL, Becker DF. Role of Proline in Pathogen and Host Interactions. Antioxid Redox Signal 2019; 30:683-709. [PMID: 29241353 PMCID: PMC6338583 DOI: 10.1089/ars.2017.7335] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Revised: 10/26/2017] [Accepted: 11/14/2017] [Indexed: 01/20/2023]
Abstract
SIGNIFICANCE Proline metabolism has complex roles in a variety of biological processes, including cell signaling, stress protection, and energy production. Proline also contributes to the pathogenesis of various disease-causing organisms. Understanding the mechanisms of how pathogens utilize proline is important for developing new strategies against infectious diseases. Recent Advances: The ability of pathogens to acquire amino acids is critical during infection. Besides protein biosynthesis, some amino acids, such as proline, serve as a carbon, nitrogen, or energy source in bacterial and protozoa pathogens. The role of proline during infection depends on the physiology of the host/pathogen interactions. Some pathogens rely on proline as a critical respiratory substrate, whereas others exploit proline for stress protection. CRITICAL ISSUES Disruption of proline metabolism and uptake has been shown to significantly attenuate virulence of certain pathogens, whereas in other pathogens the importance of proline during infection is not known. Inhibiting proline metabolism and transport may be a useful therapeutic strategy against some pathogens. Developing specific inhibitors to avoid off-target effects in the host, however, will be challenging. Also, potential treatments that target proline metabolism should consider the impact on intracellular levels of Δ1-pyrroline-5-carboxylate, a metabolite intermediate that can have opposing effects on pathogenesis. FUTURE DIRECTIONS Further characterization of how proline metabolism is regulated during infection would provide new insights into the role of proline in pathogenesis. Biochemical and structural characterization of proline metabolic enzymes from different pathogens could lead to new tools for exploring proline metabolism during infection and possibly new therapeutic compounds.
Collapse
Affiliation(s)
- Shelbi L. Christgen
- Department of Biochemistry, Redox Biology Center, University of Nebraska−Lincoln, Lincoln, Nebraska
| | - Donald F. Becker
- Department of Biochemistry, Redox Biology Center, University of Nebraska−Lincoln, Lincoln, Nebraska
| |
Collapse
|
3
|
Abstract
SIGNIFICANCE Proline catabolism refers to the 4-electron oxidation of proline to glutamate catalyzed by the enzymes proline dehydrogenase (PRODH) and l-glutamate γ-semialdehyde dehydrogenase (GSALDH, or ALDH4A1). These enzymes and the intermediate metabolites of the pathway have been implicated in tumor growth and suppression, metastasis, hyperprolinemia metabolic disorders, schizophrenia susceptibility, life span extension, and pathogen virulence and survival. In some bacteria, PRODH and GSALDH are combined into a bifunctional enzyme known as proline utilization A (PutA). PutAs are not only virulence factors in some pathogenic bacteria but also fascinating systems for studying the coordination of metabolic enzymes via substrate channeling. Recent Advances: The past decade has seen an explosion of structural data for proline catabolic enzymes. This review surveys these structures, emphasizing protein folds, substrate recognition, oligomerization, kinetic mechanisms, and substrate channeling in PutA. CRITICAL ISSUES Major unsolved structural targets include eukaryotic PRODH, the complex between monofunctional PRODH and monofunctional GSALDH, and the largest of all PutAs, trifunctional PutA. The structural basis of PutA-membrane association is poorly understood. Fundamental aspects of substrate channeling in PutA remain unknown, such as the identity of the channeled intermediate, how the tunnel system is activated, and the roles of ancillary tunnels. FUTURE DIRECTIONS New approaches are needed to study the molecular and in vivo mechanisms of substrate channeling. With the discovery of the proline cycle driving tumor growth and metastasis, the development of inhibitors of proline metabolic enzymes has emerged as an exciting new direction. Structural biology will be important in these endeavors.
Collapse
Affiliation(s)
- John J Tanner
- 1 Department of Biochemistry and University of Missouri-Columbia , Columbia, Missouri.,2 Department of Chemistry, University of Missouri-Columbia , Columbia, Missouri
| |
Collapse
|
4
|
Liu LK, Tanner JJ. Crystal Structure of Aldehyde Dehydrogenase 16 Reveals Trans-Hierarchical Structural Similarity and a New Dimer. J Mol Biol 2018; 431:524-541. [PMID: 30529746 DOI: 10.1016/j.jmb.2018.11.030] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 11/28/2018] [Accepted: 11/29/2018] [Indexed: 12/24/2022]
Abstract
The aldehyde dehydrogenase (ALDH) superfamily is a vast group of enzymes that catalyze the NAD+-dependent oxidation of aldehydes to carboxylic acids. ALDH16 is perhaps the most enigmatic member of the superfamily, owing to its extra C-terminal domain of unknown function and the absence of the essential catalytic cysteine residue in certain non-bacterial ALDH16 sequences. Herein we report the first production of recombinant ALDH16, the first biochemical characterization of ALDH16, and the first crystal structure of ALDH16. Recombinant expression systems were generated for the bacterial ALDH16 from Loktanella sp. and human ALDH16A1. Four high-resolution crystal structures of Loktanella ALDH16 were determined. Loktanella ALDH16 is found to be a bona fide enzyme, exhibiting NAD+-binding, ALDH activity, and esterase activity. In contrast, human ALDH16A1 apparently lacks measurable aldehyde oxidation activity, suggesting that it is a pseudoenzyme, consistent with the absence of the catalytic Cys in its sequence. The fold of ALDH16 comprises three domains: NAD+-binding, catalytic, and C-terminal. The latter is unique to ALDH16 and features a Rossmann fold connected to a protruding β-flap. The tertiary structural interactions of the C-terminal domain mimic the quaternary structural interactions of the classic ALDH superfamily dimer, a phenomenon we call "trans-hierarchical structural similarity." ALDH16 forms a unique dimer in solution, which mimics the classic ALDH superfamily dimer-of-dimer tetramer. Small-angle X-ray scattering shows that human ALDH16A1 has the same dimeric structure and fold as Loktanella ALDH16. We suggest that the Loktanella ALDH16 structure may be considered to be the archetype of the ALDH16 family.
Collapse
Affiliation(s)
- Li-Kai Liu
- Department of Biochemistry, University of Missouri, Columbia, MO 65211, USA
| | - John J Tanner
- Department of Biochemistry, University of Missouri, Columbia, MO 65211, USA; Department of Chemistry, University of Missouri, Columbia, MO 65211, USA.
| |
Collapse
|
5
|
Zheng R, Feng X, Wei X, Pan X, Liu C, Song R, Jin Y, Bai F, Jin S, Wu W, Cheng Z. PutA Is Required for Virulence and Regulated by PruR in Pseudomonas aeruginosa. Front Microbiol 2018; 9:548. [PMID: 29632523 PMCID: PMC5879082 DOI: 10.3389/fmicb.2018.00548] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Accepted: 03/09/2018] [Indexed: 01/08/2023] Open
Abstract
Pseudomonas aeruginosa, a Gram-negative opportunistic pathogenic bacterium, causes acute and chronic infections. Upon entering the host, P. aeruginosa alters global gene expression to adapt to host environment and avoid clearance by the host immune system. Proline utilization A (PutA) is a bifunctional enzyme, which converts proline to glutamate. Here we report that PutA was required for the virulence of P. aeruginosa in a murine acute pneumonia model. A putA mutant was more susceptible to oxidative stress compared to the wild type strain. An AraC/XylS family protein, PruR, directly bound to the upstream of −35 box in the putA promoter and activated putA expression. High concentration of proline in bacteria up-regulated pruR expression, which led to the activation of putA expression. As a feedback regulation, glutamate produced by PutA released PruR from the putA promoter and turned off the putA expression. PruR affected bacterial virulence through the regulation of the putA expression. Altogether, these data are the first to reveal that PutA plays an important role in the pathogenesis of P. aeruginosa, as well as to describe the genetic regulation of PutA in P. aeruginosa.
Collapse
Affiliation(s)
- Ruiping Zheng
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Xuemei Feng
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Xueying Wei
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Xiaolei Pan
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Chang Liu
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Ruopu Song
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Yongxin Jin
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Fang Bai
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Shouguang Jin
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China.,Department of Molecular Genetics and Microbiology, College of Medicine, University of Florida, Gainesville, FL, United States
| | - Weihui Wu
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Zhihui Cheng
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| |
Collapse
|
6
|
Liu LK, Becker DF, Tanner JJ. Structure, function, and mechanism of proline utilization A (PutA). Arch Biochem Biophys 2017; 632:142-157. [PMID: 28712849 DOI: 10.1016/j.abb.2017.07.005] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Revised: 07/11/2017] [Accepted: 07/12/2017] [Indexed: 01/13/2023]
Abstract
Proline has important roles in multiple biological processes such as cellular bioenergetics, cell growth, oxidative and osmotic stress response, protein folding and stability, and redox signaling. The proline catabolic pathway, which forms glutamate, enables organisms to utilize proline as a carbon, nitrogen, and energy source. FAD-dependent proline dehydrogenase (PRODH) and NAD+-dependent glutamate semialdehyde dehydrogenase (GSALDH) convert proline to glutamate in two sequential oxidative steps. Depletion of PRODH and GSALDH in humans leads to hyperprolinemia, which is associated with mental disorders such as schizophrenia. Also, some pathogens require proline catabolism for virulence. A unique aspect of proline catabolism is the multifunctional proline utilization A (PutA) enzyme found in Gram-negative bacteria. PutA is a large (>1000 residues) bifunctional enzyme that combines PRODH and GSALDH activities into one polypeptide chain. In addition, some PutAs function as a DNA-binding transcriptional repressor of proline utilization genes. This review describes several attributes of PutA that make it a remarkable flavoenzyme: (1) diversity of oligomeric state and quaternary structure; (2) substrate channeling and enzyme hysteresis; (3) DNA-binding activity and transcriptional repressor function; and (4) flavin redox dependent changes in subcellular location and function in response to proline (functional switching).
Collapse
Affiliation(s)
- Li-Kai Liu
- Department of Biochemistry, University of Missouri, Columbia, MO, 65211, United States
| | - Donald F Becker
- Department of Biochemistry and Redox Biology Center, University of Nebraska-Lincoln, Lincoln, NE, 68588-0664, United States.
| | - John J Tanner
- Department of Biochemistry, University of Missouri, Columbia, MO, 65211, United States; Department of Chemistry, University of Missouri, Columbia, MO, 65211, United States.
| |
Collapse
|
7
|
Korasick DA, Gamage TT, Christgen S, Stiers KM, Beamer LJ, Henzl MT, Becker DF, Tanner JJ. Structure and characterization of a class 3B proline utilization A: Ligand-induced dimerization and importance of the C-terminal domain for catalysis. J Biol Chem 2017; 292:9652-9665. [PMID: 28420730 PMCID: PMC5465489 DOI: 10.1074/jbc.m117.786855] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2017] [Revised: 04/12/2017] [Indexed: 12/23/2022] Open
Abstract
The bifunctional flavoenzyme proline utilization A (PutA) catalyzes the two-step oxidation of proline to glutamate using separate proline dehydrogenase (PRODH) and l-glutamate-γ-semialdehyde dehydrogenase active sites. Because PutAs catalyze sequential reactions, they are good systems for studying how metabolic enzymes communicate via substrate channeling. Although mechanistically similar, PutAs vary widely in domain architecture, oligomeric state, and quaternary structure, and these variations represent different structural solutions to the problem of sequestering a reactive metabolite. Here, we studied PutA from Corynebacterium freiburgense (CfPutA), which belongs to the uncharacterized 3B class of PutAs. A 2.7 Å resolution crystal structure showed the canonical arrangement of PRODH, l-glutamate-γ-semialdehyde dehydrogenase, and C-terminal domains, including an extended interdomain tunnel associated with substrate channeling. The structure unexpectedly revealed a novel open conformation of the PRODH active site, which is interpreted to represent the non-activated conformation, an elusive form of PutA that exhibits suboptimal channeling. Nevertheless, CfPutA exhibited normal substrate-channeling activity, indicating that it isomerizes into the active state under assay conditions. Sedimentation-velocity experiments provided insight into the isomerization process, showing that CfPutA dimerizes in the presence of a proline analog and NAD+ These results are consistent with the morpheein model of enzyme hysteresis, in which substrate binding induces conformational changes that promote assembly of a high-activity oligomer. Finally, we used domain deletion analysis to investigate the function of the C-terminal domain. Although this domain contains neither catalytic residues nor substrate sites, its removal impaired both catalytic activities, suggesting that it may be essential for active-site integrity.
Collapse
Affiliation(s)
| | | | - Shelbi Christgen
- Department of Biochemistry and Redox Biology Center, University of Nebraska, Lincoln, Nebraska 68588
| | | | | | | | - Donald F Becker
- Department of Biochemistry and Redox Biology Center, University of Nebraska, Lincoln, Nebraska 68588
| | - John J Tanner
- From the Departments of Biochemistry and
- Chemistry, University of Missouri, Columbia, Missouri 65211, and
| |
Collapse
|
8
|
Arentson BW, Hayes EL, Zhu W, Singh H, Tanner JJ, Becker DF. Engineering a trifunctional proline utilization A chimaera by fusing a DNA-binding domain to a bifunctional PutA. Biosci Rep 2016; 36:e00413. [PMID: 27742866 PMCID: PMC5293562 DOI: 10.1042/bsr20160435] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Revised: 10/05/2016] [Accepted: 10/14/2016] [Indexed: 01/18/2023] Open
Abstract
Proline utilization A (PutA) is a bifunctional flavoenzyme with proline dehydrogenase (PRODH) and Δ1-pyrroline-5-carboxylate (P5C) dehydrogenase (P5CDH) domains that catalyses the two-step oxidation of proline to glutamate. Trifunctional PutAs also have an N-terminal ribbon-helix-helix (RHH) DNA-binding domain and moonlight as autogenous transcriptional repressors of the put regulon. A unique property of trifunctional PutA is the ability to switch functions from DNA-bound repressor to membrane-associated enzyme in response to cellular nutritional needs and proline availability. In the present study, we attempt to construct a trifunctional PutA by fusing the RHH domain of Escherichia coli PutA (EcRHH) to the bifunctional Rhodobacter capsulatus PutA (RcPutA) in order to explore the modular design of functional switching in trifunctional PutAs. The EcRHH-RcPutA chimaera retains the catalytic properties of RcPutA while acquiring the oligomeric state, quaternary structure and DNA-binding properties of EcPutA. Furthermore, the EcRHH-RcPutA chimaera exhibits proline-induced lipid association, which is a fundamental characteristic of functional switching. Unexpectedly, RcPutA lipid binding is also activated by proline, which shows for the first time that bifunctional PutAs exhibit a limited form of functional switching. Altogether, these results suggest that the C-terminal domain (CTD), which is conserved by trifunctional PutAs and certain bifunctional PutAs, is essential for functional switching in trifunctional PutAs.
Collapse
Affiliation(s)
- Benjamin W Arentson
- Department of Biochemistry, Redox Biology Center, University of Nebraska-Lincoln, Lincoln, NE 68588, U.S.A
| | - Erin L Hayes
- Department of Biochemistry, Redox Biology Center, University of Nebraska-Lincoln, Lincoln, NE 68588, U.S.A
| | - Weidong Zhu
- Department of Biochemistry, Redox Biology Center, University of Nebraska-Lincoln, Lincoln, NE 68588, U.S.A
| | - Harkewal Singh
- Department of Chemistry, University of Missouri-Columbia, Columbia, MO 65211, U.S.A
- Protein Technologies and Assays, Research and Development, MilliporeSigma, 2909 Laclede Avenue, St. Louis, MO 63103, U.S.A
| | - John J Tanner
- Department of Biochemistry, University of Missouri-Columbia, Columbia, MO 65211, U.S.A
- Department of Chemistry, University of Missouri-Columbia, Columbia, MO 65211, U.S.A
| | - Donald F Becker
- Department of Biochemistry, Redox Biology Center, University of Nebraska-Lincoln, Lincoln, NE 68588, U.S.A.
| |
Collapse
|
9
|
Sehgal SA. Pharmacoinformatics and molecular docking studies reveal potential novel Proline Dehydrogenase (PRODH) compounds for Schizophrenia inhibition. Med Chem Res 2016. [DOI: 10.1007/s00044-016-1752-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
|
10
|
Abstract
Virulence gene expression serves two main functions, growth in/on the host, and the acquisition of nutrients. Therefore, it is obvious that nutrient availability is important to control expression of virulence genes. In any cell, enzymes are the components that are best informed about the availability of their respective substrates and products. It is thus not surprising that bacteria have evolved a variety of strategies to employ this information in the control of gene expression. Enzymes that have a second (so-called moonlighting) function in the regulation of gene expression are collectively referred to as trigger enzymes. Trigger enzymes may have a second activity as a direct regulatory protein that can bind specific DNA or RNA targets under particular conditions or they may affect the activity of transcription factors by covalent modification or direct protein-protein interaction. In this chapter, we provide an overview on these mechanisms and discuss the relevance of trigger enzymes for virulence gene expression in bacterial pathogens.
Collapse
|
11
|
Luo M, Christgen S, Sanyal N, Arentson BW, Becker DF, Tanner JJ. Evidence that the C-terminal domain of a type B PutA protein contributes to aldehyde dehydrogenase activity and substrate channeling. Biochemistry 2014; 53:5661-73. [PMID: 25137435 PMCID: PMC4159212 DOI: 10.1021/bi500693a] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
![]()
Proline utilization A (PutA) is a
bifunctional enzyme that catalyzes
the oxidation of proline to glutamate. Structures of type A PutAs
have revealed the catalytic core consisting of proline dehydrogenase
(PRODH) and Δ1-pyrroline-5-carboxylate dehydrogenase
(P5CDH) modules connected by a substrate-channeling tunnel. Type B
PutAs also have a C-terminal domain of unknown function (CTDUF) that
is absent in type A PutAs. Small-angle X-ray scattering (SAXS), mutagenesis,
and kinetics are used to determine the contributions of this domain
to PutA structure and function. The 1127-residue Rhodobacter
capsulatus PutA (RcPutA) is used as a representative CTDUF-containing
type B PutA. The reaction progress curve for the coupled PRODH–P5CDH
activity of RcPutA does not exhibit a time lag, implying a substrate
channeling mechanism. RcPutA is monomeric in solution, which is unprecedented
for PutAs. SAXS rigid body modeling with target–decoy validation
is used to build a model of RcPutA. On the basis of homology to aldehyde
dehydrogenases (ALDHs), the CTDUF is predicted to consist of a β-hairpin
fused to a noncatalytic Rossmann fold domain. The predicted tertiary
structural interactions of the CTDUF resemble the quaternary structural
interactions in the type A PutA dimer interface. The model is tested
by mutagenesis of the dimerization hairpin of a type A PutA and the
CTDUF hairpin of RcPutA. Similar functional phenotypes are observed
in the two sets of variants, supporting the hypothesis that the CTDUF
mimics the type A PutA dimer interface. These results suggest annotation
of the CTDUF as an ALDH superfamily domain that facilitates P5CDH
activity and substrate channeling by stabilizing the aldehyde-binding
site and sealing the substrate-channeling tunnel from the bulk medium.
Collapse
Affiliation(s)
- Min Luo
- Department of Chemistry, University of Missouri-Columbia , Columbia, Missouri 65211, United States
| | | | | | | | | | | |
Collapse
|
12
|
Structures of the PutA peripheral membrane flavoenzyme reveal a dynamic substrate-channeling tunnel and the quinone-binding site. Proc Natl Acad Sci U S A 2014; 111:3389-94. [PMID: 24550478 DOI: 10.1073/pnas.1321621111] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Proline utilization A (PutA) proteins are bifunctional peripheral membrane flavoenzymes that catalyze the oxidation of L-proline to L-glutamate by the sequential activities of proline dehydrogenase and aldehyde dehydrogenase domains. Located at the inner membrane of Gram-negative bacteria, PutAs play a major role in energy metabolism by coupling the oxidation of proline imported from the environment to the reduction of membrane-associated quinones. Here, we report seven crystal structures of the 1,004-residue PutA from Geobacter sulfurreducens, along with determination of the protein oligomeric state by small-angle X-ray scattering and kinetic characterization of substrate channeling and quinone reduction. The structures reveal an elaborate and dynamic tunnel system featuring a 75-Å-long tunnel that links the two active sites and six smaller tunnels that connect the main tunnel to the bulk medium. The locations of these tunnels and their responses to ligand binding and flavin reduction suggest hypotheses about how proline, water, and quinones enter the tunnel system and where L-glutamate exits. Kinetic measurements show that glutamate production from proline occurs without a lag phase, consistent with substrate channeling and implying that the observed tunnel is functionally relevant. Furthermore, the structure of reduced PutA complexed with menadione bisulfite reveals the elusive quinone-binding site. The benzoquinone binds within 4.0 Å of the flavin si face, consistent with direct electron transfer. The location of the quinone site implies that the concave surface of the PutA dimer approaches the membrane. Altogether, these results provide insight into how PutAs couple proline oxidation to quinone reduction.
Collapse
|
13
|
Monteoliva MI, Rizzi YS, Cecchini NM, Hajirezaei MR, Alvarez ME. Context of action of proline dehydrogenase (ProDH) in the Hypersensitive Response of Arabidopsis. BMC PLANT BIOLOGY 2014; 14:21. [PMID: 24410747 PMCID: PMC3902764 DOI: 10.1186/1471-2229-14-21] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2013] [Accepted: 01/08/2014] [Indexed: 05/19/2023]
Abstract
BACKGROUND Proline (Pro) dehydrogenase (ProDH) potentiates the oxidative burst and cell death of the plant Hypersensitive Response (HR) by mechanisms not yet elucidated. ProDH converts Pro into ∆1 pyrroline-5-carboxylate (P5C) and can act together with P5C dehydrogenase (P5CDH) to produce Glu, or with P5C reductase (P5CR) to regenerate Pro and thus stimulate the Pro/P5C cycle. To better understand the effects of ProDH in HR, we studied the enzyme at three stages of the defense response differing in their ROS and cell death levels. In addition, we tested if ProDH requires P5CDH to potentiate HR. RESULTS Control and infected leaves of wild type and p5cdh plants were used to monitor ProDH activity, in vivo Pro catabolism, amino acid content, and gene expression. Wild type plants activated ProDH at all HR stages. They did not consume Pro during maximal ROS accumulation, and maintained almost basal P5C levels at all conditions. p5cdh mutants activated ProDH as wild type plants. They achieved maximum oxidative burst and cell death levels producing normal HR lesions, but evidenced premature defense activation. CONCLUSION ProDH activation has different effects on HR. Before the oxidative burst it leads to Pro consumption involving the action of P5CDH. During the oxidative burst, ProDH becomes functionally uncoupled to P5CDH and apparently works with P5CR. The absence of P5CDH does not reduce ROS, cell death, or pathogen resistance, indicating this enzyme is not accompanying ProDH in the potentiation of these defense responses. In contrast, p5cdh infected plants displayed increased ROS burst and earlier initiation of HR cell death. In turn, our results suggest that ProDH may sustain HR by participating in the Pro/P5C cycle, whose action on HR must be formally evaluated in a future.
Collapse
Affiliation(s)
- Mariela Inés Monteoliva
- Centro de Investigaciones en Química Biológica de Córdoba CIQUIBIC, UNC-CONICET, Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Ciudad Universitaria, X5000HUA Córdoba, Argentina
| | - Yanina Soledad Rizzi
- Centro de Investigaciones en Química Biológica de Córdoba CIQUIBIC, UNC-CONICET, Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Ciudad Universitaria, X5000HUA Córdoba, Argentina
| | - Nicolás Miguel Cecchini
- Centro de Investigaciones en Química Biológica de Córdoba CIQUIBIC, UNC-CONICET, Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Ciudad Universitaria, X5000HUA Córdoba, Argentina
| | - Mohammad-Reza Hajirezaei
- Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Molecular Plant Nutrition, Corrensstrasse 3, 06466 Gatersleben, Germany
| | - María Elena Alvarez
- Centro de Investigaciones en Química Biológica de Córdoba CIQUIBIC, UNC-CONICET, Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Ciudad Universitaria, X5000HUA Córdoba, Argentina
| |
Collapse
|
14
|
Abstract
SIGNIFICANCE The imino acid proline is utilized by different organisms to offset cellular imbalances caused by environmental stress. The wide use in nature of proline as a stress adaptor molecule indicates that proline has a fundamental biological role in stress response. Understanding the mechanisms by which proline enhances abiotic/biotic stress response will facilitate agricultural crop research and improve human health. RECENT ADVANCES It is now recognized that proline metabolism propels cellular signaling processes that promote cellular apoptosis or survival. Studies have shown that proline metabolism influences signaling pathways by increasing reactive oxygen species (ROS) formation in the mitochondria via the electron transport chain. Enhanced ROS production due to proline metabolism has been implicated in the hypersensitive response in plants, lifespan extension in worms, and apoptosis, tumor suppression, and cell survival in animals. CRITICAL ISSUES The ability of proline to influence disparate cellular outcomes may be governed by ROS levels generated in the mitochondria. Defining the threshold at which proline metabolic enzyme expression switches from inducing survival pathways to cellular apoptosis would provide molecular insights into cellular redox regulation by proline. Are ROS the only mediators of proline metabolic signaling or are other factors involved? FUTURE DIRECTIONS New evidence suggests that proline biosynthesis enzymes interact with redox proteins such as thioredoxin. An important future pursuit will be to identify other interacting partners of proline metabolic enzymes to uncover novel regulatory and signaling networks of cellular stress response.
Collapse
Affiliation(s)
- Xinwen Liang
- Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, NE 68588, USA
| | | | | | | |
Collapse
|
15
|
Scazzocchio C. In praise of erroneous hypotheses. Fungal Genet Biol 2013; 58-59:126-31. [PMID: 23973960 DOI: 10.1016/j.fgb.2013.08.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Accepted: 08/13/2013] [Indexed: 11/18/2022]
Abstract
In the sixties Cove and Pateman discovered that mutants of Aspergillus nidulans lacking nitrate reductase activity were constitutive for the expression of genes induced by nitrate and dependent on the transcription factor NirA. They proposed that the nitrate protein acted as a repressor, preventing the transcription factor activity of NirA. Nitrate-mediated regulation behaved similarly in other organisms. This "autogenous regulation hypothesis" has recently shown to be erroneous, in the very organism for which it was first proposed. Nevertheless this erroneous hypothesis have led to a thorough dissection of the process of regulation of nitrate assimilation and more importantly to a hypothesis bearing on the origin of metabolite-responsive transcription factors. In this article I discuss the heuristic value and evolutionary importance of autogenous regulation.
Collapse
Affiliation(s)
- Claudio Scazzocchio
- Department of Microbiology, Imperial College, London SW7 2AZ, United Kingdom; Institut de Génétique et Microbiologie, CNRS UMR 8621, Université Paris-Sud, 91405 Orsay, France.
| |
Collapse
|
16
|
Luo M, Singh RK, Tanner JJ. Structural determinants of oligomerization of δ(1)-pyrroline-5-carboxylate dehydrogenase: identification of a hexamerization hot spot. J Mol Biol 2013; 425:3106-20. [PMID: 23747974 DOI: 10.1016/j.jmb.2013.05.027] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2013] [Revised: 05/30/2013] [Accepted: 05/31/2013] [Indexed: 11/17/2022]
Abstract
The aldehyde dehydrogenase (ALDH) superfamily member Δ(1)-pyrroline-5-carboxylate dehydrogenase (P5CDH) catalyzes the NAD(+)-dependent oxidation of glutamate semialdehyde to glutamate, which is the final step of proline catabolism. Defects in P5CDH activity lead to the metabolic disorder type II hyperprolinemia, P5CDH is essential for virulence of the fungal pathogen Cryptococcus neoformans, and bacterial P5CDHs have been targeted for vaccine development. Although the enzyme oligomeric state is known to be important for ALDH function, the oligomerization of P5CDH has remained relatively unstudied. Here we determine the oligomeric states and quaternary structures of four bacterial P5CDHs using a combination of small-angle X-ray scattering, X-ray crystallography, and dynamic light scattering. The P5CDHs from Thermus thermophilus and Deinococcus radiodurans form trimer-of-dimers hexamers in solution, which is the first observation of a hexameric ALDH in solution. In contrast, two Bacillus P5CDHs form dimers in solution but do not assemble into a higher-order oligomer. Site-directed mutagenesis was used to identify a hexamerization hot spot that is centered on an arginine residue in the NAD(+)-binding domain. Mutation of this critical Arg residue to Ala in either of the hexameric enzymes prevents hexamer formation in solution. Paradoxically, the dimeric Arg-to-Ala T. thermophilus mutant enzyme packs as a hexamer in the crystal state, which illustrates the challenges associated with predicting the biological assembly in solution from crystal structures. The observation of different oligomeric states among P5CDHs suggests potential differences in cooperativity and protein-protein interactions.
Collapse
Affiliation(s)
- Min Luo
- Department of Chemistry, University of Missouri-Columbia, Columbia, MO 65211, USA
| | | | | |
Collapse
|
17
|
Luo M, Arentson BW, Srivastava D, Becker DF, Tanner JJ. Crystal structures and kinetics of monofunctional proline dehydrogenase provide insight into substrate recognition and conformational changes associated with flavin reduction and product release. Biochemistry 2012; 51:10099-108. [PMID: 23151026 DOI: 10.1021/bi301312f] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Proline dehydrogenase (PRODH) catalyzes the FAD-dependent oxidation of proline to Δ(1)-pyrroline-5-carboxylate, which is the first step of proline catabolism. Here, we report the structures of proline dehydrogenase from Deinococcus radiodurans in the oxidized state complexed with the proline analogue L-tetrahydrofuroic acid and in the reduced state with the proline site vacant. The analogue binds against the si face of the FAD isoalloxazine and is protected from bulk solvent by helix α8 and the β1-α1 loop. The FAD ribityl chain adopts two conformations in the E-S complex, which is unprecedented for flavoenzymes. One of the conformations is novel for the PRODH superfamily and may contribute to the low substrate affinity of Deinococcus PRODH. Reduction of the crystalline enzyme-inhibitor complex causes profound structural changes, including 20° butterfly bending of the isoalloxazine, crankshaft rotation of the ribityl, shifting of α8 by 1.7 Å, reconfiguration of the β1-α1 loop, and rupture of the Arg291-Glu64 ion pair. These changes dramatically open the active site to facilitate product release and allow electron acceptors access to the reduced flavin. The structures suggest that the ion pair, which is conserved in the PRODH superfamily, functions as the active site gate. Mutagenesis of Glu64 to Ala decreases the catalytic efficiency 27-fold, which demonstrates the importance of the gate. Mutation of Gly63 decreases the efficiency 140-fold, which suggests that flexibility of the β1-α1 loop is essential for optimal catalysis. The large conformational changes that are required to form the E-S complex suggest that conformational selection plays a role in substrate recognition.
Collapse
Affiliation(s)
- Min Luo
- Department of Chemistry, University of Missouri-Columbia, Columbia, MO 65211, USA
| | | | | | | | | |
Collapse
|