Interactions of PIN and PGP auxin transport mechanisms

2007 ◽  
Vol 35 (1) ◽  
pp. 137-141 ◽  
Author(s):  
A. Bandyopadhyay ◽  
J.J. Blakeslee ◽  
O.R. Lee ◽  
J. Mravec ◽  
M. Sauer ◽  
...  
Keyword(s):  
Abc Transporters ◽  
Plant Hormone ◽  
Auxin Transport ◽  
Protein Complexes ◽  
Transport Mechanisms ◽  
In Planta ◽  
P Glycoprotein ◽  
Polarized Transport ◽  
Major Facilitator ◽  
And Function

Polarized transport of the plant hormone auxin influences multiple growth processes in plants and is regulated by plasma-membrane-localized efflux and uptake carriers. The PGP (P-glycoprotein) ABC transporters (ATP-binding-cassette transporters), PIN (pin-formed) subfamily of major facilitator proteins and members of AUX/LAX families have been shown to independently transport auxin both in planta and in heterologous systems. However, PIN- and PGP-mediated transport in heterologous systems exhibits decreased substrate specificity and inhibitor-sensitivity compared with what is seen in plants and plant cells. To determine whether PIN–PGP interactions enhance transport specificity, we analysed interactions of the representative auxin-transporting PGPs with PIN1 and AUX1 in planta and in heterologous systems. Here, we provide evidence that PINs and PGPs interact and function both independently and co-ordinately to control polar auxin transport and impart transport specificity and directionality. These interactions take place in protein complexes stabilized by PGPs in detergent-resistant microdomains.

scholarly journals Auxin-transporting ABC transporters are defined by a conserved D/E-P motif regulated by a prolylisomerase

2020 ◽  
Vol 295 (37) ◽  
pp. 13094-13105 ◽  
Author(s):  
Pengchao Hao ◽  
Jian Xia ◽  
Jie Liu ◽  
Martin Di Donato ◽  
Konrad Pakula ◽  
...  
Keyword(s):  
Abc Transporters ◽  
Plant Hormone ◽  
Auxin Transport ◽  
Physical Interaction ◽  
Transport Activity ◽  
Nucleotide Binding Domain ◽  
Higher Plant ◽  
Ppiase Activity ◽  
Auxin Distribution ◽  
A Cell

The plant hormone auxin must be transported throughout plants in a cell-to-cell manner to affect its various physiological functions. ABCB transporters are critical for this polar auxin distribution, but the regulatory mechanisms controlling their function is not fully understood. The auxin transport activity of ABCB1 was suggested to be regulated by a physical interaction with FKBP42/Twisted Dwarf1 (TWD1), a peptidylprolyl cis-trans isomerase (PPIase), but all attempts to demonstrate such a PPIase activity by TWD1 have failed so far. By using a structure-based approach, we identified several surface-exposed proline residues in the nucleotide binding domain and linker of Arabidopsis ABCB1, mutations of which do not alter ABCB1 protein stability or location but do affect its transport activity. P1008 is part of a conserved signature D/E-P motif that seems to be specific for auxin-transporting ABCBs, which we now refer to as ATAs. Mutation of the acidic residue also abolishes auxin transport activity by ABCB1. All higher plant ABCBs for which auxin transport has been conclusively proven carry this conserved motif, underlining its predictive potential. Introduction of this D/E-P motif into malate importer, ABCB14, increases both its malate and its background auxin transport activity, suggesting that this motif has an impact on transport capacity. The D/E-P1008 motif is also important for ABCB1-TWD1 interactions and activation of ABCB1-mediated auxin transport by TWD1. In summary, our data imply a new function for TWD1 acting as a putative activator of ABCB-mediated auxin transport by cis-trans isomerization of peptidyl-prolyl bonds.

scholarly journals Relative Contribution of PIN-containing Secretory Vesicles and Plasma Membrane PINs to the Directed Auxin Transport: Theoretical Estimation

2018 ◽  
Author(s):  
Sander Hille ◽  
Maria Akhmanova ◽  
Matouš Glanc ◽  
Alexander Johnson ◽  
Jiří Friml
Keyword(s):  
Plasma Membrane ◽  
Auxin Transport ◽  
Secretory Vesicle ◽  
Secretory Vesicles ◽  
Transport Mechanisms ◽  
In Planta ◽  
Major Mechanism ◽  
Relative Contribution ◽  
Secretory Transport ◽  
Auxin Flux

Intercellular transport of auxin is driven by PIN-formed (PIN) proteins. PINs are localized at the plasma membrane (PM) and on constitutively recycling endomembrane vesicles. Therefore, PINs can mediate auxin transport either by direct translocation across the PM or by pumping it into secretory vesicles (SVs), leading to its secretory release upon fusion with the PM. Which of these two mechanisms dominates is a matter of debate. Here we addressed the issue with a mathematical modeling approach. We demonstrate that the efficiency of secretory transport depends on SV size, half-life of PINs on the PM, pH, exocytosis frequency and PIN density. 3D-SIM microscopy was used to determine PIN density on the PM. Combing this data with published values of the other parameters, we show that the transport activity of PINs in SVs would have to be at least 1000x greater than on the PM in order to produce a comparable macroscopic auxin transport. If both transport mechanisms operated simultaneously and PINs were equally active on SVs and PM, the contribution of secretion to the total auxin flux would be negligible. In conclusion, while secretory vesicle-mediated transport of auxin is intriguing and theoretically possible model, it unlikely to be a major mechanism of auxin transport in planta.

scholarly journals Regulation von ABC-Transportern durch FKBPs

BIOspektrum ◽  
2021 ◽  
Vol 27 (2) ◽  
pp. 131-134
Author(s):  
Markus Geisler
Keyword(s):  
Abc Transporter ◽  
Abc Transporters ◽  
Plant Hormone ◽  
Auxin Transport ◽  
Current Knowledge ◽  
Binding Protein ◽  
Atp Binding ◽  
Fk506 Binding Protein ◽  
Atp Binding Cassette

AbstractThe plant hormone auxin is distributed in the plant by a sophisticated network of importers and exporters, including members of the ABCB subclass of ATP-binding cassette (ABC) transporters. ABCB-mediated auxin transport is controlled by Twisted Dwarf1, a member of the FK506-binding protein (FKBP) family. Here, we summarize current knowledge on ABC transporter regulation by FKBPs, which seems to be conserved over kingdoms and ABC subfamilies arguing for conserved mechanism of plant and mammalian post-translational transporter regulation.

Structure of contact sites between the outer and inner mitochondrial membranes investigated by HVEM tomography

1996 ◽  
Vol 54 ◽  
pp. 966-967
Author(s):  
C.A. Mannella ◽  
K.F. Buttle ◽  
K.A. O‘Farrell ◽  
A. Leith ◽  
M. Marko
Keyword(s):  
Liver Mitochondrion ◽  
Adenine Nucleotide ◽  
Protein Complexes ◽  
Mitochondrial Membranes ◽  
Electron Microscopic ◽  
Contact Sites ◽  
Transmission Electron ◽  
Precursor Proteins ◽  
Membrane Contacts ◽  
And Function

Early transmission electron microscopy of plastic-embedded, thin-sectioned mitochondria indicated that there are numerous junctions between the outer and inner membranes of this organelle. More recent studies have suggested that the mitochondrial membrane contacts may be the site of protein complexes engaged in specialized functions, e.g., import of mitochondrial precursor proteins, adenine nucleotide channeling, and even intermembrane signalling. It has been suggested that the intermembrane contacts may be sites of membrane fusion involving non-bilayer lipid domains in the two membranes. However, despite growing interest in the nature and function of intramitochondrial contact sites, little is known about their structure.We are using electron microscopic tomography with the Albany HVEM to determine the internal organization of mitochondria. We have reconstructed a 0.6-μm section through an isolated, plasticembedded rat-liver mitochondrion by combining 123 projections collected by tilting (+/- 70°) around two perpendicular tilt axes. The resulting 3-D image has confirmed the basic inner-membrane organization inferred from lower-resolution reconstructions obtained from single-axis tomography.

Chaperonin as the normal controls and pathological anti-stress response in the human reproductive system

2016 ◽  
pp. 126-129
Author(s):  
M. Makarenko ◽  
◽  
D. Hovsyeyev ◽  
L. Sydoryk ◽  
◽  
...  
Keyword(s):  
Reproductive System ◽  
Stress Proteins ◽  
Physiological Stress ◽  
Protein Complexes ◽  
Reproductive Function ◽  
Intercellular Signaling ◽  
Toll Like Receptors ◽  
Wide Range ◽  
Protein Functions ◽  
And Function

Different kinds of physiological stress cause mass changes in the cells, including the changes in the structure and function of the protein complexes and in separate molecules. The protein functions is determined by its folding (the spatial conclusion), which depends on the functioning of proteins of thermal shock- molecular chaperons (HSPs) or depends on the stress proteins, that are high-conservative; specialized proteins that are responsible for the correct proteinaceous folding. The family of the molecular chaperones/ chaperonins/ Hsp60 has a special place due to the its unique properties of activating the signaling cascades through the system of Toll-like receptors; it also stimulates the cells to produce anti- inflammatory cytokines, defensins, molecules of cell adhesion and the molecules of MHC; it functions as the intercellular signaling molecule. The pathological role of Hsp60 is established in a wide range of illnesses, from diabetes to atherosclerosis, where Hsp60 takes part in the regulation of both apoptosis and the autoimmune processes. The presence of the HSPs was found in different tissues that are related to the reproductive system. Key words: molecular chaperons (HSPs), Toll-like receptors, reproductive function, natural auto antibody.

scholarly journals The NALCN Channel Regulator UNC-80 Functions in a Subset of Interneurons To Regulate Caenorhabditis elegans Reversal Behavior

2019 ◽  
Vol 10 (1) ◽  
pp. 199-210 ◽  
Author(s):  
Chuanman Zhou ◽  
Jintao Luo ◽  
Xiaohui He ◽  
Qian Zhou ◽  
Yunxia He ◽  
...  
Keyword(s):  
Plant Hormone ◽  
Neuronal Excitability ◽  
Resting Membrane Potential ◽  
Loss Of Function ◽  
Wild Type ◽  
C Elegans ◽  
Link Type ◽  
Complex Functions ◽  
And Function ◽  
Multiple Loss

NALCN (Na+leak channel, non-selective) is a conserved, voltage-insensitive cation channel that regulates resting membrane potential and neuronal excitability. UNC79 and UNC80 are key regulators of the channel function. However, the behavioral effects of the channel complex are not entirely clear and the neurons in which the channel functions remain to be identified. In a forward genetic screen for C. elegans mutants with defective avoidance response to the plant hormone methyl salicylate (MeSa), we isolated multiple loss-of-function mutations in unc-80 and unc-79. C. elegans NALCN mutants exhibited similarly defective MeSa avoidance. Interestingly, NALCN, unc-80 and unc-79 mutants all showed wild type-like responses to other attractive or repelling odorants, suggesting that NALCN does not broadly affect odor detection or related forward and reversal behaviors. To understand in which neurons the channel functions, we determined the identities of a subset of unc-80-expressing neurons. We found that unc-79 and unc-80 are expressed and function in overlapping neurons, which verified previous assumptions. Neuron-specific transgene rescue and knockdown experiments suggest that the command interneurons AVA and AVE and the anterior guidepost neuron AVG can play a sufficient role in mediating unc-80 regulation of the MeSa avoidance. Though primarily based on genetic analyses, our results further imply that MeSa might activate NALCN by direct or indirect actions. Altogether, we provide an initial look into the key neurons in which the NALCN channel complex functions and identify a novel function of the channel in regulating C. elegans reversal behavior through command interneurons.

scholarly journals Pichia pastoris and the Recombinant Human Heterodimeric Amino Acid Transporter 4F2hc-LAT1: From Clone Selection to Pure Protein

2021 ◽  
Vol 4 (3) ◽  
pp. 51
Author(s):  
Satish Kantipudi ◽  
Daniel Harder ◽  
Sara Bonetti ◽  
Dimitrios Fotiadis ◽  
Jean-Marc Jeckelmann
Keyword(s):  
Amino Acid ◽  
Pichia Pastoris ◽  
Protein Complexes ◽  
Amino Acid Transporter ◽  
Amino Acid Transporters ◽  
Expression Host ◽  
Amino Acids And Derivatives ◽  
Heterodimeric Complex ◽  
Acid Transporter ◽  
And Function

Heterodimeric amino acid transporters (HATs) are protein complexes composed of two subunits, a heavy and a light subunit belonging to the solute carrier (SLC) families SLC3 and SLC7. HATs transport amino acids and derivatives thereof across the plasma membrane. The human HAT 4F2hc-LAT1 is composed of the type-II membrane N-glycoprotein 4F2hc (SLC3A2) and the L-type amino acid transporter LAT1 (SLC7A5). 4F2hc-LAT1 is medically relevant, and its dysfunction and overexpression are associated with autism and tumor progression. Here, we provide a general applicable protocol on how to screen for the best membrane transport protein-expressing clone in terms of protein amount and function using Pichia pastoris as expression host. Furthermore, we describe an overexpression and purification procedure for the production of the HAT 4F2hc-LAT1. The isolated heterodimeric complex is pure, correctly assembled, stable, binds the substrate L-leucine, and is thus properly folded. Therefore, this Pichia pastoris-derived recombinant human 4F2hc-LAT1 sample can be used for downstream biochemical and biophysical characterizations.

scholarly journals Expression and Function of Organic Anion Transporting Polypeptides in the Human Brain: Physiological and Pharmacological Implications

Pharmaceutics ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 834
Author(s):  
Anima M. Schäfer ◽  
Henriette E. Meyer zu Schwabedissen ◽  
Markus Grube
Keyword(s):  
Organic Anion ◽  
Physiological Role ◽  
Point Of View ◽  
Efflux Transporters ◽  
Organic Anion Transporting Polypeptides ◽  
Current State ◽  
P Glycoprotein ◽  
The Central Nervous System ◽  
And Function ◽  
Uptake Transporters

The central nervous system (CNS) is an important pharmacological target, but it is very effectively protected by the blood–brain barrier (BBB), thereby impairing the efficacy of many potential active compounds as they are unable to cross this barrier. Among others, membranous efflux transporters like P-Glycoprotein are involved in the integrity of this barrier. In addition to these, however, uptake transporters have also been found to selectively uptake certain compounds into the CNS. These transporters are localized in the BBB as well as in neurons or in the choroid plexus. Among them, from a pharmacological point of view, representatives of the organic anion transporting polypeptides (OATPs) are of particular interest, as they mediate the cellular entry of a variety of different pharmaceutical compounds. Thus, OATPs in the BBB potentially offer the possibility of CNS targeting approaches. For these purposes, a profound understanding of the expression and localization of these transporters is crucial. This review therefore summarizes the current state of knowledge of the expression and localization of OATPs in the CNS, gives an overview of their possible physiological role, and outlines their possible pharmacological relevance using selected examples.

scholarly journals Stoichiometry and Turnover of the Bacterial Flagellar Switch Protein FliN

mBio ◽  
2014 ◽  
Vol 5 (4) ◽  
Author(s):  
Nicolas J. Delalez ◽  
Richard M. Berry ◽  
Judith P. Armitage
Keyword(s):  
Copy Number ◽  
Motor Proteins ◽  
Fluorescent Protein ◽  
Protein Complexes ◽  
Content Type ◽  
Rotation Direction ◽  
Cell Measurement ◽  
Biological Complexes ◽  
And Function

ABSTRACTSome proteins in biological complexes exchange with pools of free proteins while the complex is functioning. Evidence is emerging that protein exchange can be part of an adaptive mechanism. The bacterial flagellar motor is one of the most complex biological machines and is an ideal model system to study protein dynamics in large multimeric complexes. Recent studies showed that the copy number of FliM in the switch complex and the fraction of FliM that exchanges vary with the direction of flagellar rotation. Here, we investigated the stoichiometry and turnover of another switch complex component, FliN, labeled with the fluorescent protein CyPet, inEscherichia coli. Our results confirm that,in vivo, FliM and FliN form a complex with stoichiometry of 1:4 and function as a unit. We estimated that wild-type motors contained 120 ± 26 FliN molecules. Motors that rotated only clockwise (CW) or counterclockwise (CCW) contained 114 ± 17 and 144 ± 26 FliN molecules, respectively. The ratio of CCW-to-CW FliN copy numbers was 1.26, very close to that of 1.29 reported previously for FliM. We also measured the exchange of FliN molecules, which had a time scale and dependence upon rotation direction similar to those of FliM, consistent with an exchange of FliM-FliN as a unit. Our work confirms the highly dynamic nature of multimeric protein complexes and indicates that, under physiological conditions, these machines might not be the stable, complete structures suggested by averaged fixed methodologies but, rather, incomplete rings that can respond and adapt to changing environments.IMPORTANCEThe flagellum is one of the most complex structures in a bacterial cell, with the core motor proteins conserved across species. Evidence is now emerging that turnover of some of these motor proteins depends on motor activity, suggesting that turnover is important for function. The switch complex transmits the chemosensory signal to the rotor, and we show, by using single-cell measurement, that both the copy number and the fraction of exchanging molecules vary with the rotational bias of the rotor. When the motor is locked in counterclockwise rotation, the copy number is similar to that determined by averaged, fixed methodologies, but when locked in a clockwise direction, the number is much lower, suggesting that that the switch complex ring is incomplete. Our results suggest that motor remodeling is an important component in tuning responses and adaptation at the motor.

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