Membrane Structural Biology

Luckey, Mary

doi:10.1017/cbo9780511811098

Cited by 108 publications

(71 citation statements)

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“…This results in two spatially adjacent cysteine residues which form a bulky surface in transmembrane helices. Such a bulky helix surface might be important in mediating helix-helix interactions, as knob-to-hole helix packing has been reported as a key folding process in many studies (e.g., [1,35]). three distinct subtrees, according to the topology states is obvious.…”

Section: High Propensitymentioning

confidence: 99%

“…Active nutrient transport, signal and energy transduction, and ion flow are only a few of the numerous functions enabled by membrane proteins [1]. Membrane proteins obtain their specific functionality by individual folding and interactions with the hydrophobic membrane environment as well as, in many cases, by oligomeric complex formation and protein-protein interactions [1,2]. The identification of such complexes and interactions is valuable, since, on the one hand, detailed information of the function of an unknown membrane protein can be obtained by analysing its interactions with proteins of known function.…”

Section: Introductionmentioning

confidence: 99%

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Structure Topology Prediction of Discriminative Sequence Motifs in Membrane Proteins with Domains of Unknown Functions

2013

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Motivation. Membrane proteins play essential roles in cellular processes of organisms. Photosynthesis, transport of ions and small molecules, signal transduction, and light harvesting are examples of processes which are realised by membrane proteins and contribute to a cell's specificity and functionality. The analysis of membrane proteins has shown to be an important part in the understanding of complex biological processes. Genome-wide investigations of membrane proteins have revealed a large number of short, distinct sequence motifs. Results. The in silico analysis of 32 membrane protein families with domains of unknown functions discussed in this study led to a novel approach which describes the separation of motifs by residue-specific distributions. Based on these distributions, the topology structure of the majority of motifs in hypothesised membrane proteins with unknown topology can be predicted. Conclusion. We hypothesise that short sequence motifs can be separated into structure-forming motifs on the one hand, as such motifs show high prediction accuracy in all investigated protein families. This points to their general importance in -helical membrane protein structure formation and interaction mediation. On the other hand, motifs which show high prediction accuracies only in certain families can be classified as functionally important and relevant for family-specific functional characteristics.

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Section: High Propensitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Structure Topology Prediction of Discriminative Sequence Motifs in Membrane Proteins with Domains of Unknown Functions

2013

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“…The relationship between structure and function of biological membranes is a subject of great biophysical and pharmaceutical interest. Physical and functional properties of biological membranes strongly depend on the structure of the membrane components and their arrangement and Abbreviations: CL, cardiolipin; cryoTEM, cryo-transmission electron microscopy; DMPE, 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine; DMPG, 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol; DPPE, 1,2-dipalmitoylsn-glycero-3-phosphoethanolamine; DPPG, 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol; E. coli, Escherichia coli; P, packing parameter; PE, phosphatidylethanolamine; PG, phosphatidylglycerol; TMCL, 1 0 ,3 0 -bis[1,2-dimyristoyl-snglycero-3-phospho]-sn-glycerol; T m , main transition temperature distribution within the bilayer [1][2][3][4]. The chemical structure of the lipids is of particular importance for biomembrane functions.…”

Section: Introductionmentioning

confidence: 99%

Morphological changes of bacterial model membrane vesicles

Meister

Finger

Hause

et al. 2014

Euro J Lipid Sci & Tech

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Unilamellar vesicles frequently serve as model membrane systems to study membrane‐peptide and membrane‐protein interactions. They are formed either from natural lipid extracts that contain complex lipid mixtures, or from synthetic one‐, two‐, or multi‐component lipid mixtures mimicking the lipid composition of biological membranes. Unilamellar vesicles can be prepared by extrusion of aqueous multilamellar phospholipid suspensions and they can have limited stability due to aggregation and fusion processes. We used cryo‐transmission electron microscopy (cryoTEM) to study the morphology of vesicles of phosphatidylethanolamines (PEs), phosphatidylglycerols (PGs), and cardiolipins (CLs) that represent the major lipid components of cytoplasmic membranes of Gram‐negative bacteria. Our results show that single‐component vesicles of PE and PG stored at RT are stable in shape and size for at least 1 wk. In contrast, two‐component vesicles of PE/PG and PE/CL transform into lamellar sheets already several hours after preparation, which is probably due to a compensation of different spontaneous curvatures of PG lipids compared to PE and CL. With this investigation we intend to alert researchers working with model membranes to scrutinize the shape and stability of vesicles before using them in protein‐vesicle interaction studies. Practical applications: Liposomes represent widely‐used model membrane systems that are applied to mimic natural membranes. Usually, these liposomes are composed of one or two lipid components representing the major lipid constituents of the respective natural membrane. Their long‐term shape, aggregation, and fusion stability is an important prerequisite for the study of peptide‐liposome and protein‐liposome interactions, where the binding of peptides or proteins can have serious impacts on the liposomal shape and size. Furthermore, shape and size stability is of outstanding importance for the application of liposomes as drug‐delivery system. We showed that single‐component liposomes composed of the major lipid components of cytoplasmic membranes of Gram‐negative bacteria (PE and PG) are stable in shape and size for at least 1 wk, whereas the corresponding two‐component liposomes become unstable within hours and transform into discs and sheets. This knowledge will be indispensable for future studies on interactions of liposomes with peptides and proteins. Cryo‐transmission electron microscopy is the method of choice to study the size, morphology, and shape stability of liposomes being composed of the phospholipids PE, PG, and CL that represent the major lipid components of cytoplasmic membranes of Gram‐negative bacteria.

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“…Their universal applicability has become apparent more recently. In simple photoautotrophs, light-driven proton gradients involve bacteriorhodopsin [65], while in more advanced eukaryotes, an electron transport chain generates mitochondrial proton gradients. Proton pumps and their regulation are thus at the epicenter of plant growth that, stripped to its bare essentials, depend on three morphogen gradients, auxin, protons and Ca 2+ rather than just two.…”

Section: D'arcy Thompson Alan Turing and Peter Mitchell Revisitedmentioning

confidence: 99%

Phyllotaxis Turns Over a New Leaf—A New Hypothesis

Lamport

Held

et al. 2020

IJMS

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Phyllotaxis describes the periodic arrangement of plant organs most conspicuously floral. Oscillators generally underlie periodic phenomena. A hypothetical algorithm generates phyllotaxis regulated by the Hechtian growth oscillator of the stem apical meristem (SAM) protoderm. The oscillator integrates biochemical and mechanical force that regulate morphogenetic gradients of three ionic species, auxin, protons and Ca 2+ . Hechtian adhesion between cell wall and plasma membrane transduces wall stress that opens Ca 2+ channels and reorients auxin efflux "PIN" proteins; they control the auxin-activated proton pump that dissociates Ca 2+ bound by periplasmic arabinogalactan proteins (AGP-Ca 2+ ) hence the source of cytosolic Ca 2+ waves that activate exocytosis of wall precursors, AGPs and PIN proteins essential for morphogenesis. This novel approach identifies the critical determinants of an algorithm that generates phyllotaxis spiral and Fibonaccian symmetry: these determinants in order of their relative contribution are: (1) size of the apical meristem and the AGP-Ca 2+ capacitor; (2) proton pump activity; (3) auxin efflux proteins; (4) Ca 2+ channel activity; (5) Hechtian adhesion that mediates the cell wall stress vector. Arguably, AGPs and the AGP-Ca 2+ capacitor plays a decisive role in phyllotaxis periodicity and its evolutionary origins.Int. J. Mol. Sci. 2020, 21, 1145 2 of 15 stress-strain to the plasma membrane where an auxin-activated proton pump dissociates AGP-Ca 2+ . Elevated cytosolic Ca 2+ -activates exocytosis thus regulating plant growth. Discussion of the Hechtian Oscillator vis-a-vis the role of the primary cell wall in plant morphogenesis [2] suggests extrapolating the oscillator to phyllotaxis based on the premise that presence of the oscillator components implies the presence of a functional Hechtian Oscillator. Indeed, recent work suggests the mechanotransduction of stress relocates auxin efflux PIN proteins that generate new protoderm primordia. However, the precise biochemical mechanisms involved in stress transduction and the role of auxin and calcium homeostasis remain to be elucidated. Here, we invoke Hechtian adhesion and AGPs as essential components that lead us to propose a novel biochemical algorithm for floral phyllotaxis and an explanation of its strong tendency towards a periodic series first described by Fibonacci (1170Fibonacci ( -1240. This approach contrasts with many previous studies with an overwhelming mathematical bias. Indeed, many observations in Nature involve periodicity and the probable underlying oscillations Oscillatory plant growth, known since Darwin [3], was subsequently confirmed by rapid tip growth of pollen tubes and root hairs [4]. Plant morphogenesis also involves periodicity strikingly displayed by the pattern of leaves and floral organs [5] that often appear as Fibonacci spirals typified by whorls of 3, 5, 8, 13, 21 and 34 petals [6]. Hypothetically, such periodicity depends on an underlying oscillator such as the recently formulated Hechtian growth oscilla...

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Membrane Structural Biology

Cited by 108 publications

References 0 publications

Structure Topology Prediction of Discriminative Sequence Motifs in Membrane Proteins with Domains of Unknown Functions

Structure Topology Prediction of Discriminative Sequence Motifs in Membrane Proteins with Domains of Unknown Functions

Morphological changes of bacterial model membrane vesicles

Phyllotaxis Turns Over a New Leaf—A New Hypothesis

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