-
Protein Science : a Publication of the... Feb 2016The AbgT family of transporters was thought to contribute to bacterial folate biosynthesis by importing the catabolite p-aminobenzoyl-glutamate for producing this... (Review)
Review
The AbgT family of transporters was thought to contribute to bacterial folate biosynthesis by importing the catabolite p-aminobenzoyl-glutamate for producing this essential vitamin. Approximately 13,000 putative transporters of the family have been identified. However, before our work, no structural information was available and even functional data were minimal for this family of membrane proteins. To elucidate the structure and function of the AbgT family of transporters, we recently determined the X-ray structures of the full-length Alcanivorax borkumensis YdaH and Neisseria gonorrhoeae MtrF membrane proteins. The structures reveal that these two transporters assemble as dimers with architectures distinct from all other families of transporters. Both YdaH and MtrF are bowl-shaped dimers with a solvent-filled basin extending from the cytoplasm halfway across the membrane bilayer. The protomers of YdaH and MtrF contain nine transmembrane helices and two hairpins. These structures directly suggest a plausible pathway for substrate transport. A combination of the crystal structure, genetic analysis and substrate accumulation assay indicates that both YdaH and MtrF behave as exporters, capable of removing the folate metabolite p-aminobenzoic acid from bacterial cells. Further experimental data based on drug susceptibility and radioactive transport assay suggest that both YdaH and MtrF participate as antibiotic efflux pumps, importantly mediating bacterial resistance to sulfonamide antimetabolite drugs. It is possible that many of these AbgT-family transporters act as exporters, thereby conferring bacterial resistance to sulfonamides. The AbgT-family transporters may be important targets for the rational design of novel antibiotics to combat bacterial infections.
Topics: Amino Acid Sequence; Anti-Bacterial Agents; Antimetabolites; Bacteria; Bacterial Proteins; Biological Transport; Crystallography, X-Ray; Folic Acid; Gene Expression Regulation, Bacterial; Membrane Transport Proteins; Models, Molecular; Molecular Sequence Data; Protein Conformation; Sequence Alignment
PubMed: 26443496
DOI: 10.1002/pro.2820 -
Research in Microbiology 2018Efflux pumps are membrane proteins which contribute to multi-drug resistance. In Gram-negative bacteria, some of these pumps form complex tripartite assemblies in... (Review)
Review
Efflux pumps are membrane proteins which contribute to multi-drug resistance. In Gram-negative bacteria, some of these pumps form complex tripartite assemblies in association with an outer membrane channel and a periplasmic membrane fusion protein. These tripartite machineries span both membranes and the periplasmic space, and they extrude from the bacterium chemically diverse toxic substrates. In this chapter, we summarise current understanding of the structural architecture, functionality, and regulation of tripartite multi-drug efflux assemblies.
Topics: Bacterial Proteins; Gram-Negative Bacteria; Membrane Transport Proteins; Models, Molecular; Protein Conformation
PubMed: 29787834
DOI: 10.1016/j.resmic.2018.05.003 -
International Journal of Molecular... Jul 2022Membrane transport proteins are widely present in all living organisms, however, their function, transported substrate, and mechanism of action are unknown. Here we use...
Membrane transport proteins are widely present in all living organisms, however, their function, transported substrate, and mechanism of action are unknown. Here we use diverse bioinformatics tools to investigate the evolution of MTPs, analyse domain organisation and loop topology, and study the comparative alignment of modelled 3D structures. Our results suggest a high level of conservancy between MTPs from different taxa on both amino acids and structural levels, which imply some degree of functional similarities. The presence of loop/s of different lengths in various positions suggests tax-on-specific adaptation to transported substrates, intracellular localisation, accessibility for post-translation modifications, and interaction with other proteins. The comparison of modelled structures proposes close relations and a common origin for MTP and Na/H exchanger. Further, a high level of amino acid similarity and identity between archaeal and bacterial MTPs and Na/H exchangers imply conservancy of ion transporting function at least for archaeal and bacterial MTPs.
Topics: Amino Acid Sequence; Biological Transport; Ion Transport; Membrane Transport Proteins; Sodium-Hydrogen Exchangers
PubMed: 35897663
DOI: 10.3390/ijms23158094 -
Metallomics : Integrated Biometal... Jul 2018Virtually all organisms require iron and have evolved to obtain this element in free or chelated forms. Under anaerobic or low pH conditions commonly encountered by... (Review)
Review
Virtually all organisms require iron and have evolved to obtain this element in free or chelated forms. Under anaerobic or low pH conditions commonly encountered by numerous pathogens, iron predominantly exists in the ferrous (Fe2+) form. The ferrous iron transport (Feo) system is the only widespread mechanism dedicated solely to bacterial ferrous iron import, and this system has been linked to pathogenic virulence, bacterial colonization, and microbial survival. The canonical feo operon encodes for three proteins that comprise the Feo system: FeoA, a small cytoplasmic β-barrel protein; FeoB, a large, polytopic membrane protein with a soluble G-protein domain capable of hydrolyzing GTP; and FeoC, a small, cytoplasmic protein containing a winged-helix motif. While previous studies have revealed insight into soluble and fragmentary domains of the Feo system, the chief membrane-bound component FeoB remains poorly studied. However, recent advances have demonstrated that large quantities of intact FeoB can be overexpressed, purified, and biophysically characterized, revealing glimpses into FeoB function. Two models of full-length FeoB have been published, providing starting points for hypothesis-driven investigations into the mechanism of FeoB-mediated ferrous iron transport. Finally, in vivo studies have begun to shed light on how this system functions as a unique multicomponent complex. In light of these new data, this review will summarize what is known about the Feo system, including recent advancements in FeoB structure and function.
Topics: Cation Transport Proteins; Cell Membrane; Escherichia coli Proteins; Ferrous Compounds; Gene Expression Regulation, Bacterial; Ion Transport; Iron; Membrane Transport Proteins; Operon; Protein Conformation; Virulence
PubMed: 29953152
DOI: 10.1039/c8mt00097b -
Protein Science : a Publication of the... Oct 2015Major facilitator superfamily (MFS) is a large class of secondary active transporters widely expressed across all life kingdoms. Although a common 12-transmembrane... (Review)
Review
Major facilitator superfamily (MFS) is a large class of secondary active transporters widely expressed across all life kingdoms. Although a common 12-transmembrane helix-bundle architecture is found in most MFS crystal structures available, a common mechanism of energy coupling remains to be elucidated. Here, we discuss several models for energy-coupling in the transport process of the transporters, largely based on currently available structures and the results of their biochemical analyses. Special attention is paid to the interaction between protonation and the negative-inside membrane potential. Also, functional roles of the conserved sequence motifs are discussed in the context of the 3D structures. We anticipate that in the near future, a unified picture of the functions of MFS transporters will emerge from the insights gained from studies of the common architectures and conserved motifs.
Topics: Binding Sites; Biological Transport; Crystallography, X-Ray; Energy Metabolism; Membrane Transport Proteins; Models, Biological; Protein Conformation
PubMed: 26234418
DOI: 10.1002/pro.2759 -
Biomolecules Dec 2020The translocases of the mitochondrial outer and inner membranes, the TOM and TIMs, import hundreds of nucleus-encoded proteins into mitochondria. TOM and TIMs are... (Review)
Review
The translocases of the mitochondrial outer and inner membranes, the TOM and TIMs, import hundreds of nucleus-encoded proteins into mitochondria. TOM and TIMs are multi-subunit protein complexes that work in cooperation with other complexes to import proteins in different sub-mitochondrial destinations. The overall architecture of these protein complexes is conserved among yeast/fungi, animals, and plants. Recent studies have revealed unique characteristics of this machinery, particularly in the eukaryotic supergroup Excavata. Despite multiple differences, homologues of Tim17, an essential component of one of the TIM complexes and a member of the Tim17/Tim22/Tim23 family, have been found in all eukaryotes. Here, we review the structure and function of Tim17 and Tim17-containing protein complexes in different eukaryotes, and then compare them to the single homologue of this protein found in , a unicellular parasitic protozoan.
Topics: Animals; Cell Nucleus; Conserved Sequence; Fungi; Gene Expression; Humans; Membrane Transport Proteins; Mitochondria; Mitochondrial Membrane Transport Proteins; Mitochondrial Membranes; Mitochondrial Precursor Protein Import Complex Proteins; Mitochondrial Proteins; Multiprotein Complexes; Plants; Protein Binding; Protein Structure, Secondary; Protein Transport; Trypanosoma brucei brucei
PubMed: 33297490
DOI: 10.3390/biom10121643 -
The Journal of Biological Chemistry Apr 2023Tapasin (Tsn) plays a critical role in antigen processing and presentation by major histocompatibility complex class I (MHC-I) molecules. The mechanism of Tsn-mediated... (Review)
Review
Tapasin (Tsn) plays a critical role in antigen processing and presentation by major histocompatibility complex class I (MHC-I) molecules. The mechanism of Tsn-mediated peptide loading and exchange hinges on the conformational dynamics governing the interaction of Tsn and MHC-I with recent structural and functional studies pinpointing the critical sites of direct or allosteric regulation. In this review, we highlight these recent findings and relate them to the extensive molecular and cellular data that are available for these evolutionary interdependent proteins. Furthermore, allotypic differences of MHC-I with regard to the editing and chaperoning function of Tsn are reviewed and related to the mechanistic observations. Finally, evolutionary aspects of the mode of action of Tsn will be discussed, a short comparison with the Tsn-related molecule TAPBPR (Tsn-related protein) will be given, and the impact of Tsn on noncanonical MHC-I molecules will be described.
Topics: Antigen Presentation; Histocompatibility Antigens Class I; Immunoglobulins; Membrane Transport Proteins
PubMed: 36758805
DOI: 10.1016/j.jbc.2023.102987 -
Journal of Molecular Biology Aug 2021Infectious diseases present a major threat to public health globally. Pathogens can acquire resistance to anti-infectious agents via several means including... (Review)
Review
Infectious diseases present a major threat to public health globally. Pathogens can acquire resistance to anti-infectious agents via several means including transporter-mediated efflux. Typically, multidrug transporters feature spacious, dynamic, and chemically malleable binding sites to aid in the recognition and transport of chemically diverse substrates across cell membranes. Here, we discuss recent structural investigations of multidrug transporters involved in resistance to infectious diseases that belong to the ATP-binding cassette (ABC) superfamily, the major facilitator superfamily (MFS), the drug/metabolite transporter (DMT) superfamily, the multidrug and toxic compound extrusion (MATE) family, the small multidrug resistance (SMR) family, and the resistance-nodulation-division (RND) superfamily. These structural insights provide invaluable information for understanding and combatting multidrug resistance.
Topics: ATP-Binding Cassette Transporters; Anti-Infective Agents; Drug Resistance, Microbial; Drug Resistance, Multiple; Humans; Membrane Transport Proteins; Structure-Activity Relationship
PubMed: 33891902
DOI: 10.1016/j.jmb.2021.167005 -
Biochimica Et Biophysica Acta.... Apr 2018Structural biology has advanced our understanding of membrane proteins like no other scientific discipline in the past two decades and the number of high resolution... (Review)
Review
Structural biology has advanced our understanding of membrane proteins like no other scientific discipline in the past two decades and the number of high resolution membrane transporter structures solved by X-ray crystallography has increased exponentially over this time period. Currently, single particle cryo-EM is in full swing due to a recent resolution revolution and permits for structural insights of proteins that were refractory to crystallization. It is foreseeable that multiple structures of many human transporters will be solved in the coming five years. Nevertheless, many scientifically important questions remain unanswered despite of available structures, as is illustrated in this article at the example of multidrug efflux pumps and ABC transporters. Structure-function studies likely continue to be a supporting pillar of membrane transporter research. However, there is a trend towards the "integrated structural biologist", whose research focusses on a biological question and who closely collaborates with other research groups specialized in spectroscopy techniques or molecular dynamics simulation. Future membrane protein research requires joint efforts from specialists of various disciplines to finally work towards a molecular understanding of membrane transport in the context of the living cell. This article is part of a Special Issue entitled: Beyond the Structure-Function Horizon of Membrane Proteins edited by Ute Hellmich, Rupak Doshi and Benjamin McIlwain.
Topics: Biological Transport; Cryoelectron Microscopy; Crystallography, X-Ray; Forecasting; Humans; Membrane Transport Proteins; Molecular Dynamics Simulation; Protein Conformation; Research; Structure-Activity Relationship
PubMed: 28867210
DOI: 10.1016/j.bbamem.2017.08.009 -
Current Opinion in Structural Biology Aug 2015Cells from all domains of life encode energy-dependent trans-membrane transporters that can expel harmful substances including clinically applied therapeutic agents. As... (Review)
Review
Cells from all domains of life encode energy-dependent trans-membrane transporters that can expel harmful substances including clinically applied therapeutic agents. As a collective body, these transporters perform as a super-system that confers tolerance to an enormous range of harmful compounds and consequently aid survival in hazardous environments. In the Gram-negative bacteria, some of these transporters serve as energy-transducing components of tripartite assemblies that actively efflux drugs and other harmful compounds, as well as deliver virulence agents across the entire cell envelope. We draw together recent structural and functional data to present the current models for the transport mechanisms for the main classes of multi-drug transporters and their higher-order assemblies.
Topics: ATP-Binding Cassette Transporters; Anti-Bacterial Agents; Bacterial Proteins; Cell Membrane; Cell Wall; Drug Resistance, Multiple, Bacterial; Gram-Negative Bacteria; Membrane Transport Proteins; Protein Conformation
PubMed: 26282926
DOI: 10.1016/j.sbi.2015.07.015