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Selim KA, Alva V. PII-like signaling proteins: a new paradigm in orchestrating cellular homeostasis. Curr Opin Microbiol 2024; 79:102453. [PMID: 38678827 DOI: 10.1016/j.mib.2024.102453] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Revised: 02/19/2024] [Accepted: 02/20/2024] [Indexed: 05/01/2024]
Abstract
Members of the PII superfamily are versatile, multitasking signaling proteins ubiquitously found in all domains of life. They adeptly monitor and synchronize the cell's carbon, nitrogen, energy, redox, and diurnal states, primarily by binding interdependently to adenyl-nucleotides, including charged nucleotides (ATP, ADP, and AMP) and second messengers such as Cyclic adenosine monophosphate, Cyclic di-adenosine monophosphate, and S-adenosylmethionine-AMP (SAM-AMP). These proteins also undergo a variety of posttranslational modifications, such as phosphorylation, adenylation, uridylation, carboxylation, and disulfide bond formation, which further provide cues on the metabolic state of the cell. Serving as precise metabolic sensors, PII superfamily proteins transmit this information to diverse cellular targets, establishing dynamic regulatory assemblies that fine-tune cellular homeostasis. Recently discovered, PII-like proteins are emerging families of signaling proteins that, while related to canonical PII proteins, have evolved to fulfill a diverse range of cellular functions, many of which remain elusive. In this review, we focus on the evolution of PII-like proteins and summarize the molecular mechanisms governing the assembly dynamics of PII complexes, with a special emphasis on the PII-like protein SbtB.
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Affiliation(s)
- Khaled A Selim
- Microbiology / Molecular Physiology of Prokaryotes, Institute of Biology II, University of Freiburg, Schänzlestraße 1, 79104 Freiburg, Germany; Protein Evolution Department, Max Planck Institute for Biology Tübingen, 72076 Tübingen, Germany.
| | - Vikram Alva
- Protein Evolution Department, Max Planck Institute for Biology Tübingen, 72076 Tübingen, Germany
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Mantovani O, Haffner M, Walke P, Elshereef AA, Wagner B, Petras D, Forchhammer K, Selim KA, Hagemann M. The redox-sensitive R-loop of the carbon control protein SbtB contributes to the regulation of the cyanobacterial CCM. Sci Rep 2024; 14:7885. [PMID: 38570698 PMCID: PMC10991534 DOI: 10.1038/s41598-024-58354-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [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: 08/24/2023] [Accepted: 03/28/2024] [Indexed: 04/05/2024] Open
Abstract
SbtB is a PII-like protein that regulates the carbon-concentrating mechanism (CCM) in cyanobacteria. SbtB proteins can bind many adenyl nucleotides and possess a characteristic C-terminal redox sensitive loop (R-loop) that forms a disulfide bridge in response to the diurnal state of the cell. SbtBs also possess an ATPase/ADPase activity that is modulated by the redox-state of the R-loop. To investigate the R-loop in the cyanobacterium Synechocystis sp. PCC 6803, site-specific mutants, unable to form the hairpin and permanently in the reduced state, and a R-loop truncation mutant, were characterized under different inorganic carbon (Ci) and light regimes. Growth under diurnal rhythm showed a role of the R-loop as sensor for acclimation to changing light conditions. The redox-state of the R-loop was found to impact the binding of the adenyl-nucleotides to SbtB, its membrane association and thereby the CCM regulation, while these phenotypes disappeared after truncation of the R-loop. Collectively, our data imply that the redox-sensitive R-loop provides an additional regulatory layer to SbtB, linking the CO2-related signaling activity of SbtB with the redox state of cells, mainly reporting the actual light conditions. This regulation not only coordinates CCM activity in the diurnal rhythm but also affects the primary carbon metabolism.
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Affiliation(s)
- Oliver Mantovani
- Department of Plant Physiology, Institute of Biosciences, University of Rostock, A.-Einstein-Str. 3, 18059, Rostock, Germany
| | - Michael Haffner
- Interfaculty Institute of Microbiology and Infection Medicine Tübingen, University of Tübingen, Tübingen, Germany
| | - Peter Walke
- Department of Plant Physiology, Institute of Biosciences, University of Rostock, A.-Einstein-Str. 3, 18059, Rostock, Germany
| | - Abdalla A Elshereef
- Interfaculty Institute of Microbiology and Infection Medicine Tübingen, University of Tübingen, Tübingen, Germany
- Chemistry of Natural and Microbial Products Department, Pharmaceutical and Drug Industries Research Institute, National Research Centre, Giza, Egypt
| | - Berenike Wagner
- Interfaculty Institute of Microbiology and Infection Medicine Tübingen, University of Tübingen, Tübingen, Germany
| | - Daniel Petras
- Interfaculty Institute of Microbiology and Infection Medicine Tübingen, University of Tübingen, Tübingen, Germany
| | - Karl Forchhammer
- Interfaculty Institute of Microbiology and Infection Medicine Tübingen, University of Tübingen, Tübingen, Germany
| | - Khaled A Selim
- Interfaculty Institute of Microbiology and Infection Medicine Tübingen, University of Tübingen, Tübingen, Germany.
- Department of Protein Evolution, Max Planck Institute for Biology, Tübingen, Germany.
- Institute of Biology, Microbiology/Molecular Physiology of Prokaryotes, University of Freiburg, Schänzlestraße 1, 79104, Freiburg, Germany.
| | - Martin Hagemann
- Department of Plant Physiology, Institute of Biosciences, University of Rostock, A.-Einstein-Str. 3, 18059, Rostock, Germany.
- Interdisciplinary Faculty, Department Life, Light and Matter, University of Rostock, Rostock, Germany.
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Llop A, Labella JI, Borisova M, Forchhammer K, Selim KA, Contreras A. Pleiotropic effects of PipX, PipY, or RelQ overexpression on growth, cell size, photosynthesis, and polyphosphate accumulation in the cyanobacterium Synechococcus elongatus PCC7942. Front Microbiol 2023; 14:1141775. [PMID: 37007489 PMCID: PMC10060972 DOI: 10.3389/fmicb.2023.1141775] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Accepted: 02/23/2023] [Indexed: 03/18/2023] Open
Abstract
The cyanobacterial protein PipY belongs to the Pyridoxal-phosphate (PLP)-binding proteins (PLPBP/COG0325) family of pyridoxal-phosphate-binding proteins, which are represented in all three domains of life. These proteins share a high degree of sequence conservation, appear to have purely regulatory functions, and are involved in the homeostasis of vitamin B6 vitamers and amino/keto acids. Intriguingly, the genomic context of the pipY gene in cyanobacteria connects PipY with PipX, a protein involved in signaling the intracellular energy status and carbon-to-nitrogen balance. PipX regulates its cellular targets via protein–protein interactions. These targets include the PII signaling protein, the ribosome assembly GTPase EngA, and the transcriptional regulators NtcA and PlmA. PipX is thus involved in the transmission of multiple signals that are relevant for metabolic homeostasis and stress responses in cyanobacteria, but the exact function of PipY is still elusive. Preliminary data indicated that PipY might also be involved in signaling pathways related to the stringent stress response, a pathway that can be induced in the unicellular cyanobacterium Synechococcus elongatus PCC7942 by overexpression of the (p)ppGpp synthase, RelQ. To get insights into the cellular functions of PipY, we performed a comparative study of PipX, PipY, or RelQ overexpression in S. elongatus PCC7942. Overexpression of PipY or RelQ caused similar phenotypic responses, such as growth arrest, loss of photosynthetic activity and viability, increased cell size, and accumulation of large polyphosphate granules. In contrast, PipX overexpression decreased cell length, indicating that PipX and PipY play antagonistic roles on cell elongation or cell division. Since ppGpp levels were not induced by overexpression of PipY or PipX, it is apparent that the production of polyphosphate in cyanobacteria does not require induction of the stringent response.
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Affiliation(s)
- Antonio Llop
- Departamento de Fisiología, Genética y Microbiología, Facultad de Ciencias, Universidad de Alicante, Alicante, Spain
- Interfaculty Institute for Microbiology and Infection Medicine, Organismic Interactions Department, Cluster of Excellence 'Controlling Microbes to Fight Infections', University of Tübingen, Tübingen, Germany
| | - Jose I. Labella
- Departamento de Fisiología, Genética y Microbiología, Facultad de Ciencias, Universidad de Alicante, Alicante, Spain
| | - Marina Borisova
- Interfaculty Institute for Microbiology and Infection Medicine, Organismic Interactions Department, Cluster of Excellence 'Controlling Microbes to Fight Infections', University of Tübingen, Tübingen, Germany
| | - Karl Forchhammer
- Interfaculty Institute for Microbiology and Infection Medicine, Organismic Interactions Department, Cluster of Excellence 'Controlling Microbes to Fight Infections', University of Tübingen, Tübingen, Germany
| | - Khaled A. Selim
- Interfaculty Institute for Microbiology and Infection Medicine, Organismic Interactions Department, Cluster of Excellence 'Controlling Microbes to Fight Infections', University of Tübingen, Tübingen, Germany
| | - Asunción Contreras
- Departamento de Fisiología, Genética y Microbiología, Facultad de Ciencias, Universidad de Alicante, Alicante, Spain
- *Correspondence: Asunción Contreras,
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Selim KA, Haffner M, Mantovani O, Albrecht R, Zhu H, Hagemann M, Forchhammer K, Hartmann MD. Carbon signaling protein SbtB possesses atypical redox-regulated apyrase activity to facilitate regulation of bicarbonate transporter SbtA. Proc Natl Acad Sci U S A 2023; 120:e2205882120. [PMID: 36800386 PMCID: PMC9974498 DOI: 10.1073/pnas.2205882120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [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: 04/04/2022] [Accepted: 12/15/2022] [Indexed: 02/18/2023] Open
Abstract
The PII superfamily consists of widespread signal transduction proteins found in all domains of life. In addition to canonical PII proteins involved in C/N sensing, structurally similar PII-like proteins evolved to fulfill diverse, yet poorly understood cellular functions. In cyanobacteria, the bicarbonate transporter SbtA is co-transcribed with the conserved PII-like protein, SbtB, to augment intracellular inorganic carbon levels for efficient CO2 fixation. We identified SbtB as a sensor of various adenine nucleotides including the second messenger nucleotides cyclic AMP (cAMP) and c-di-AMP. Moreover, many SbtB proteins possess a C-terminal extension with a disulfide bridge of potential redox-regulatory function, which we call R-loop. Here, we reveal an unusual ATP/ADP apyrase (diphosphohydrolase) activity of SbtB that is controlled by the R-loop. We followed the sequence of hydrolysis reactions from ATP over ADP to AMP in crystallographic snapshots and unravel the structural mechanism by which changes of the R-loop redox state modulate apyrase activity. We further gathered evidence that this redox state is controlled by thioredoxin, suggesting that it is generally linked to cellular metabolism, which is supported by physiological alterations in site-specific mutants of the SbtB protein. Finally, we present a refined model of how SbtB regulates SbtA activity, in which both the apyrase activity and its redox regulation play a central role. This highlights SbtB as a central switch point in cyanobacterial cell physiology, integrating not only signals from the energy state (adenyl-nucleotide binding) and the carbon supply via cAMP binding but also from the day/night status reported by the C-terminal redox switch.
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Affiliation(s)
- Khaled A. Selim
- Interfaculty Institute of Microbiology and Infection Medicine, Organismic Interactions Department, Cluster of Excellence 'Controlling Microbes to Fight Infections', Tübingen University, 72076Tübingen, Germany
- Department of Protein Evolution, Max Planck Institute for Biology, 72076Tübingen, Germany
| | - Michael Haffner
- Interfaculty Institute of Microbiology and Infection Medicine, Organismic Interactions Department, Cluster of Excellence 'Controlling Microbes to Fight Infections', Tübingen University, 72076Tübingen, Germany
| | - Oliver Mantovani
- Plant Physiology Department, Institute of Biological Sciences, Rostock University, 18059Rostock, Germany
| | - Reinhard Albrecht
- Department of Protein Evolution, Max Planck Institute for Biology, 72076Tübingen, Germany
| | - Hongbo Zhu
- Department of Protein Evolution, Max Planck Institute for Biology, 72076Tübingen, Germany
| | - Martin Hagemann
- Plant Physiology Department, Institute of Biological Sciences, Rostock University, 18059Rostock, Germany
| | - Karl Forchhammer
- Interfaculty Institute of Microbiology and Infection Medicine, Organismic Interactions Department, Cluster of Excellence 'Controlling Microbes to Fight Infections', Tübingen University, 72076Tübingen, Germany
| | - Marcus D. Hartmann
- Department of Protein Evolution, Max Planck Institute for Biology, 72076Tübingen, Germany
- Interfaculty Institute of Biochemistry, Tübingen University, 72076Tübingen, Germany
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Babele PK, Srivastava A, Selim KA, Kumar A. Millet-inspired systems metabolic engineering of NUE in crops. Trends Biotechnol 2022; 41:701-713. [PMID: 36566140 DOI: 10.1016/j.tibtech.2022.10.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Revised: 10/20/2022] [Accepted: 10/27/2022] [Indexed: 12/24/2022]
Abstract
The use of nitrogen (N) fertilizers in agriculture has a great ability to increase crop productivity. However, their excessive use has detrimental effects on the environment. Therefore, it is necessary to develop crop varieties with improved nitrogen use efficiency (NUE) that require less N but have substantial yields. Orphan crops such as millets are cultivated in limited regions and are well adapted to lower input conditions. Therefore, they serve as a rich source of beneficial traits that can be transferred into major crops to improve their NUE. This review highlights the tremendous potential of systems biology to unravel the enzymes and pathways involved in the N metabolism of millets, which can open new possibilities to generate transgenic crops with improved NUE.
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Affiliation(s)
- Piyoosh K Babele
- Rani Lakshmi Bai Central Agricultural University, Jhansi 284003, Uttar Pradesh, India.
| | - Amit Srivastava
- University of Jyväskylä, Nanoscience Centre, Department of Biological and Environmental Science, 40014 Jyväskylä, Finland
| | - Khaled A Selim
- Organismic Interactions Department, Interfaculty Institute for Microbiology and Infection Medicine, Cluster of Excellence 'Controlling Microbes to Fight Infections', Tübingen University, Auf der Morgenstelle 28, 72076 Tübingen, Germany
| | - Anil Kumar
- Rani Lakshmi Bai Central Agricultural University, Jhansi 284003, Uttar Pradesh, India
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Forchhammer K, Selim KA, Huergo LF. New views on PII signaling: from nitrogen sensing to global metabolic control. Trends Microbiol 2022. [DOI: 10.1016/j.tim.2021.12.014] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Revised: 12/21/2021] [Accepted: 12/22/2021] [Indexed: 11/20/2022]
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Selim KA, Haffner M, Burkhardt M, Mantovani O, Neumann N, Albrecht R, Seifert R, Krüger L, Stülke J, Hartmann MD, Hagemann M, Forchhammer K. Diurnal metabolic control in cyanobacteria requires perception of second messenger signaling molecule c-di-AMP by the carbon control protein SbtB. Sci Adv 2021; 7:eabk0568. [PMID: 34878830 PMCID: PMC8654305 DOI: 10.1126/sciadv.abk0568] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Because of their photosynthesis-dependent lifestyle, cyanobacteria evolved sophisticated regulatory mechanisms to adapt to oscillating day-night metabolic changes. How they coordinate the metabolic switch between autotrophic and glycogen-catabolic metabolism in light and darkness is poorly understood. Recently, c-di-AMP has been implicated in diurnal regulation, but its mode of action remains elusive. To unravel the signaling functions of c-di-AMP in cyanobacteria, we isolated c-di-AMP receptor proteins. Thereby, the carbon-sensor protein SbtB was identified as a major c-di-AMP receptor, which we confirmed biochemically and by x-ray crystallography. In search for the c-di-AMP signaling function of SbtB, we found that both SbtB and c-di-AMP cyclase–deficient mutants showed reduced diurnal growth and that c-di-AMP–bound SbtB interacts specifically with the glycogen-branching enzyme GlgB. Accordingly, both mutants displayed impaired glycogen synthesis during the day and impaired nighttime survival. Thus, the pivotal role of c-di-AMP in day-night acclimation can be attributed to SbtB-mediated regulation of glycogen metabolism.
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Affiliation(s)
- Khaled A. Selim
- Organismic Interactions Department, Interfaculty Institute for Microbiology and Infection Medicine, Cluster of Excellence ‘Controlling Microbes to Fight Infections’, Tübingen University, Auf der Morgenstelle 28, 72076 Tübingen, Germany
- Department of Protein Evolution, Max Planck Institute for Developmental Biology, Tübingen, Germany
- Corresponding author. (K.A.S.); (K.F.)
| | - Michael Haffner
- Organismic Interactions Department, Interfaculty Institute for Microbiology and Infection Medicine, Cluster of Excellence ‘Controlling Microbes to Fight Infections’, Tübingen University, Auf der Morgenstelle 28, 72076 Tübingen, Germany
| | - Markus Burkhardt
- Organismic Interactions Department, Interfaculty Institute for Microbiology and Infection Medicine, Cluster of Excellence ‘Controlling Microbes to Fight Infections’, Tübingen University, Auf der Morgenstelle 28, 72076 Tübingen, Germany
| | - Oliver Mantovani
- Plant Physiology Department, Institute of Biological Sciences, Rostock University, Rostock, Germany
| | - Niels Neumann
- Organismic Interactions Department, Interfaculty Institute for Microbiology and Infection Medicine, Cluster of Excellence ‘Controlling Microbes to Fight Infections’, Tübingen University, Auf der Morgenstelle 28, 72076 Tübingen, Germany
| | - Reinhard Albrecht
- Department of Protein Evolution, Max Planck Institute for Developmental Biology, Tübingen, Germany
| | - Roland Seifert
- Institute of Pharmacology, Hannover Medical School, Hannover, Germany
| | - Larissa Krüger
- Department of General Microbiology, Göttingen Center for Molecular Biosciences (GZMB), Göttingen University, Göttingen, Germany
| | - Jörg Stülke
- Department of General Microbiology, Göttingen Center for Molecular Biosciences (GZMB), Göttingen University, Göttingen, Germany
| | - Marcus D. Hartmann
- Department of Protein Evolution, Max Planck Institute for Developmental Biology, Tübingen, Germany
| | - Martin Hagemann
- Plant Physiology Department, Institute of Biological Sciences, Rostock University, Rostock, Germany
| | - Karl Forchhammer
- Organismic Interactions Department, Interfaculty Institute for Microbiology and Infection Medicine, Cluster of Excellence ‘Controlling Microbes to Fight Infections’, Tübingen University, Auf der Morgenstelle 28, 72076 Tübingen, Germany
- Corresponding author. (K.A.S.); (K.F.)
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Selim KA, Ermilova E, Forchhammer K. From cyanobacteria to Archaeplastida: new evolutionary insights into PII signalling in the plant kingdom. New Phytol 2020; 227:722-731. [PMID: 32077495 DOI: 10.1111/nph.16492] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Accepted: 02/13/2020] [Indexed: 05/20/2023]
Abstract
The PII superfamily consists of signal transduction proteins found in all domains of life. Canonical PII proteins sense the cellular energy state through the competitive binding of ATP and ADP, and carbon/nitrogen balance through 2-oxoglutarate binding. The ancestor of Archaeplastida inherited its PII signal transduction protein from an ancestral cyanobacterial endosymbiont. Over the course of evolution, plant PII proteins acquired a glutamine-sensing C-terminal extension, subsequently present in all Chloroplastida PII proteins. The PII proteins of various algal strains (red, green and nonphotosynthetic algae) have been systematically investigated with respect to their sensory and regulatory properties. Comparisons of the PII proteins from different phyla of oxygenic phototrophs (cyanobacteria, red algae, Chlorophyta and higher plants) have yielded insights into their evolutionary conservation vs adaptive properties. The highly conserved role of the controlling enzyme of arginine biosynthesis, N-acetyl-l-glutamate kinase (NAGK), as a main PII-interactor has been demonstrated across oxygenic phototrophs of cyanobacteria and Archaeplastida. In addition, the PII signalling system of red algae has been identified as an evolutionary intermediate between that of Cyanobacteria and Chloroplastida. In this review, we consider recent advances in understanding metabolic signalling by PII proteins of the plant kingdom.
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Affiliation(s)
- Khaled A Selim
- Organismic Interactions Department, Interfaculty Institute of Microbiology and Infection Medicine, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 28, 72076, Tübingen, Germany
| | - Elena Ermilova
- Biological Faculty, Saint-Petersburg State University, Universitetskaya nab. 7/9, Saint-Petersburg, 199034, Russia
| | - Karl Forchhammer
- Organismic Interactions Department, Interfaculty Institute of Microbiology and Infection Medicine, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 28, 72076, Tübingen, Germany
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Selim KA, Tremiño L, Marco-Marín C, Alva V, Espinosa J, Contreras A, Hartmann MD, Forchhammer K, Rubio V. Functional and structural characterization of PII-like protein CutA does not support involvement in heavy metal tolerance and hints at a small-molecule carrying/signaling role. FEBS J 2020; 288:1142-1162. [PMID: 32599651 DOI: 10.1111/febs.15464] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Revised: 04/26/2020] [Accepted: 06/01/2020] [Indexed: 12/23/2022]
Abstract
The PII-like protein CutA is annotated as being involved in Cu2+ tolerance, based on analysis of Escherichia coli mutants. However, the precise cellular function of CutA remains unclear. Our bioinformatic analysis reveals that CutA proteins are universally distributed across all domains of life. Based on sequence-based clustering, we chose representative cyanobacterial CutA proteins for physiological, biochemical, and structural characterization and examined their involvement in heavy metal tolerance, by generating CutA mutants in filamentous Nostoc sp. and in unicellular Synechococcus elongatus. However, we were unable to find any involvement of cyanobacterial CutA in metal tolerance under various conditions. This prompted us to re-examine experimentally the role of CutA in protecting E. coli from Cu2+ . Since we found no effect on copper tolerance, we conclude that CutA plays a different role that is not involved in metal protection. We resolved high-resolution CutA structures from Nostoc and S. elongatus. Similarly to their counterpart from E. coli and to canonical PII proteins, cyanobacterial CutA proteins are trimeric in solution and in crystal structure; however, no binding affinity for small signaling molecules or for Cu2+ could be detected. The clefts between the CutA subunits, corresponding to the binding pockets of PII proteins, are formed by conserved aromatic and charged residues, suggesting a conserved binding/signaling function for CutA. In fact, we find binding of organic Bis-Tris/MES molecules in CutA crystal structures, revealing a strong tendency of these pockets to accommodate cargo. This highlights the need to search for the potential physiological ligands and for their signaling functions upon binding to CutA. DATABASES: Structural data are available in Protein Data Bank (PDB) under the accession numbers 6GDU, 6GDV, 6GDW, 6GDX, 6T76, and 6T7E.
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Affiliation(s)
- Khaled A Selim
- Interfaculty Institute for Microbiology and Infection Medicine, Organismic Interactions Department, Tübingen University, Germany.,Department of Protein Evolution, Max Planck Institute for Developmental Biology, Tübingen, Germany
| | - Lorena Tremiño
- Instituto de Biomedicina de Valencia (IBV-CSIC), CIBER de Enfermedades Raras (CIBERER-ISCIII), Valencia, Spain
| | - Clara Marco-Marín
- Instituto de Biomedicina de Valencia (IBV-CSIC), CIBER de Enfermedades Raras (CIBERER-ISCIII), Valencia, Spain
| | - Vikram Alva
- Department of Protein Evolution, Max Planck Institute for Developmental Biology, Tübingen, Germany
| | - Javier Espinosa
- Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Spain
| | - Asunción Contreras
- Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Spain
| | - Marcus D Hartmann
- Department of Protein Evolution, Max Planck Institute for Developmental Biology, Tübingen, Germany
| | - Karl Forchhammer
- Interfaculty Institute for Microbiology and Infection Medicine, Organismic Interactions Department, Tübingen University, Germany
| | - Vicente Rubio
- Instituto de Biomedicina de Valencia (IBV-CSIC), CIBER de Enfermedades Raras (CIBERER-ISCIII), Valencia, Spain
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