Respiratory chain complexes in dynamic mitochondria display a patchy distribution in life cells

Background: Mitochondria, the main suppliers of cellular energy, are dynamic organelles that fuse and divide frequently. Constraining these processes impairs mitochondrial is closely linked to certain neurodegenerative diseases. It is proposed that functional mitochondrial dynamics allows the exchange of compounds thereby providing a rescue mechanism. Methodology/Principal Findings: The question discussed in this paper is whether fusion and fission of mitochondria in different cell lines result in re-localization of respiratory chain (RC) complexes and of the ATP synthase. This was addressed by fusing cells containing mitochondria with respiratory complexes labelled with different fluorescent proteins and resolving their time dependent re-localization in living cells. We found a complete reshuffling of RC complexes throughout the entire chondriome in single HeLa cells within 2–3 h by organelle fusion and fission. Polykaryons of fused cells completely re-mixed their RC complexes in 10–24 h in a progressive way. In contrast to the recently described homogeneous mixing of matrix-targeted proteins or outer membrane proteins, the distribution of RC complexes and ATP synthase in fused hybrid mitochondria, however, was not homogeneous but patterned. Thus, complete equilibration of respiratory chain complexes as integral inner mitochondrial membrane complexes is a slow process compared with matrix proteins probably limited by complete fusion. In co-expressing cells, complex II is more homogenously distributed than complex I and V, resp. Indeed, this result argues for higher mobility and less integration in supercomplexes. Conclusion/Significance: Our results clearly demonstrate that mitochondrial fusion and fission dynamics favours the re-mixing of all RC complexes within the chondriome. This permanent mixing avoids a static situation with a fixed composition of RC complexes per mitochondrion

The turnover number for band 3-mediated sulfate transport in phosphatidylcholine bilayers

AbstractThe anion transport system of the human erythrocyte membrane was reconstituted in unilamellar phosphatidylcholine vesicles, and a vesicle subpopulation of a narrow size distribution was isolated from the sample by gel filtration. In this subpopulation, the turnover number of the transport protein (the band 3 protein) for sulfate transport was determined. It was found that, in the reconstituted system, the protein transports sulfate 5–10-times faster than in the human erythrocyte membrane

Analysis of Na+-D-glucose cotransporter and other renal brush border proteins in human urine

Analysis of Na+-D-glucose cotransporter and other renal brush border proteins in human urine. A sensitive quantitative radioimmunoassay is described by which different antigens in the urine can be assayed simultaneously. Urinary excretion of three proteins from proximal tubules was compared: 1) the Na+-D-glucose cotransporter from brush border membranes and subapical vesicles; 2) a kidney-specific hydrophobic Mr 400,000 polypeptide from intermicroviUar invaginations and subapical vesicles; and 3) villin from microvilli cores. In the normal urine about 50% of the excreted Na+-D-glucose cotransporter and villin, and about 25% of the Mr 400,000 polypeptide was associated with brush border membrane vesicles, whereas trie remaining fractions of the three proteins formed small sedimentable aggregates which contained some cholesterol and fatty acids but no phospholipids. The normal urinary excretion of the Na+-D-glucose cotransporter was correlated with that of villin and the Mr 400,000 polypeptide. The data show that membrane proteins from the proximal tubule are excreted by the shedding of different brush border membrane areas. They suggest that some microvilli are released in total, and that a large fraction of the brush border membrane proteins is excreted without being associated with a phospholipid bilayer. In an attempt to define protein excretion patterns during kidney malfunctions, the excretion of brush border membrane proteins was analyzed after one intravenous injection of the X-ray contrast medium, iopamidol. No change in villin excretion was observed, but a reversible increase in the excretion of brush border membrane proteins was found in patients without diabetes. With diabetes a more pronounced iopamidol effect on the excretion of brush border membrane proteins and a significant increase in the excretion of villin was observed

A lipid-dependent link between activity and oligomerization state of the M. tuberculosis SMR protein TBsmr

AbstractTBsmr is a secondary active multidrug transporter from Mycobacterium tuberculosis that transports a plethora of compounds including antibiotics and fluorescent dyes. It belongs to the small multidrug resistance (SMR) superfamily and is structurally and functionally related to E. coli EmrE. Of particular importance is the link between protein function, oligomeric state and lipid composition. By freeze fracture EM, we found three different size distributions in three different lipid environments for TBsmr indicating different oligomeric states. The link of these states with protein activity has been probed by fluorescence spectroscopy revealing significant differences. The drug binding site has been probed further by 19F-MAS NMR through chemical labeling of native cysteine residues showing a water accessible environment in agreement with the alternating access model

Unimodality Problems in Ehrhart Theory

Ehrhart theory is the study of sequences recording the number of integer points in non-negative integral dilates of rational polytopes. For a given lattice polytope, this sequence is encoded in a finite vector called the Ehrhart $h^*$-vector. Ehrhart $h^*$-vectors have connections to many areas of mathematics, including commutative algebra and enumerative combinatorics. In this survey we discuss what is known about unimodality for Ehrhart $h^*$-vectors and highlight open questions and problems.Comment: Published in Recent Trends in Combinatorics, Beveridge, A., et al. (eds), Springer, 2016, pp 687-711, doi 10.1007/978-3-319-24298-9_27. This version updated October 2017 to correct an error in the original versio

<scp>ReSurveyEurope</scp>: A database of resurveyed vegetation plots in Europe

AbstractAimsWe introduce ReSurveyEurope — a new data source of resurveyed vegetation plots in Europe, compiled by a collaborative network of vegetation scientists. We describe the scope of this initiative, provide an overview of currently available data, governance, data contribution rules, and accessibility. In addition, we outline further steps, including potential research questions.ResultsReSurveyEurope includes resurveyed vegetation plots from all habitats. Version 1.0 of ReSurveyEurope contains 283,135 observations (i.e., individual surveys of each plot) from 79,190 plots sampled in 449 independent resurvey projects. Of these, 62,139 (78%) are permanent plots, that is, marked in situ, or located with GPS, which allow for high spatial accuracy in resurvey. The remaining 17,051 (22%) plots are from studies in which plots from the initial survey could not be exactly relocated. Four data sets, which together account for 28,470 (36%) plots, provide only presence/absence information on plant species, while the remaining 50,720 (64%) plots contain abundance information (e.g., percentage cover or cover–abundance classes such as variants of the Braun‐Blanquet scale). The oldest plots were sampled in 1911 in the Swiss Alps, while most plots were sampled between 1950 and 2020.ConclusionsReSurveyEurope is a new resource to address a wide range of research questions on fine‐scale changes in European vegetation. The initiative is devoted to an inclusive and transparent governance and data usage approach, based on slightly adapted rules of the well‐established European Vegetation Archive (EVA). ReSurveyEurope data are ready for use, and proposals for analyses of the data set can be submitted at any time to the coordinators. Still, further data contributions are highly welcome.</jats:sec

Peptide specificity and lipid activation of the lysosomal transport complex ABCB9 (TAPL)

The lysosomal ABC transporter associated with antigen processing-like (TAPL, ABCB9) acts as an ATP-dependent polypeptide transporter with broad length selectivity. To characterize in detail its substrate specificity, a procedure for functional reconstitution of human TAPL was developed. By intensive screening of detergents, ideal solubilization conditions were evolved with respect to efficiency, long term stability, and functionality of TAPL. TAPL was isolated in a two-step procedure with high purity and, subsequently, reconstituted into proteoliposomes. The peptide transport activity of reconstituted TAPL strongly depends on the lipid composition. With the help of combinatorial peptide libraries, the key positions of the peptides were localized to the N- and C-terminal residues with respect to peptide transport. At both ends, TAPL favors positively charged, aromatic, or hydrophobic residues and disfavors negatively charged residues as well as asparagine and methionine. Besides specific interactions of both terminal residues, electrostatic interactions are important, since peptides with positive net charge are more efficiently transported than negatively charged ones

Supramolecular photosystem II organization in grana thylakoid membranes: Evidence for a structured affangement

The distribution of photosystem (PS) II complexes in stacked grana thylakoids derived from electron microscopic images of freeze-fractured chloroplasts are examined for the first time using mathematical methods. These characterize the particle distribution in terms of a nearest neighbor distribution function and a pair correlation function. The data were compared with purely random distributions calculated by a Monte Carlo simulation. The analysis reveals that the PSII distribution in grana thylakoids does not correspond to a random protein mixture but that ordering forces lead to a structured arrangement on a supramolecular level. Neighboring photosystems are significantly more separated than would be the case in a purely random distribution. These results are explained by structural models, in which boundary lipids and light-harvesting complex (LHC) II trimers are arranged between neighboring PSII. Furthermore, the diffusion of PSII was analyzed by a Monte Carlo simulation with a protein density of 80% area occupation (determined for grana membranes). The mobility of the photosystems is severely reduced by the high protein density. From an estimate of the mean migration time of PSII from grana thylakoids to stroma lamellae, it becomes evident that this diffusion contributes significantly to the velocity of the repair cycle of photoinhibited PSII