162,412 research outputs found
Three-dimensional model and characterization of the iron stress-induced CP43'-photosystem I supercomplex isolated from the cyanobacterium Synechocystis PCC 6803.
No full textThe cyanobacterium Synechocystis PCC 6803 has been subjected to growth under iron-deficient conditions. As a consequence, the isiA gene is expressed, and its product, the chlorophyll a-binding protein CP43', accumulates in the cell. Recently, we have shown for the first time that 18 copies of this photosystem II (PSII)-like chlorophyll a-binding protein forms a ring around the trimeric photosystem I (PSI) reaction center (Bibby, T. S., Nield, J., and Barber, J. (2001) Nature, 412, 743-745). Here we further characterize the biochemical and structural properties of this novel CP43'-PSI supercomplex confirming that it is a functional unit of approximately 1900 kDa where the antenna size of PSI is increased by 70% or more. Using electron microscopy and single particle analysis, we have constructed a preliminary three-dimensional model of the CP43'-PSI supercomplex and used it as a framework to incorporate higher resolution structures of PSI and CP43 recently derived from x-ray crystallography. Not only does this work emphasize the flexibility of cyanobacterial light-harvesting systems in response to the lowering of phycobilisome and PSI levels under iron-deficient conditions, but it also has implications for understanding the organization of the related chlorophyll a/b-binding Pcb proteins of oxychlorobacteria, formerly known as prochlorophytes
Surface and subsurface characterisation of salt pans
No full textThis data collection bundles six datasets about the surface, subsurface and environmental conditions of saltpans that express polygonal patterns in their surface salt crust that are fully described in Lasser et al., 2020 (https://doi.org/10.5194/essd-2020-86). Information stems from 5 field sites at Badwater Basin and 21 field sites at Owens Lake – both in central California, US. All data was recorded during two field campaigns, from between November and December, 2016, and in January 2018. (1) Lasser, J., Goehring, L. (2020a). Grain size distributions of sand samples from Owens Lake and Badwater Basin in central California, collected in 2016 and 2018. PANGAEA - Data Publisher for Earth &amp; Environmental Science. https://doi.org/10.1594/PANGAEA.910996 (2) Lasser, J., Goehring, L. (2020b): Subsurface salt concentration profiles and pore water density measurements from Owens Lake, central California, measured in 2018 (Version 2). PANGAEA, https://doi.org/10.1594/PANGAEA.922264 (3) Lasser, J., Goehring, L., Nield, J. M. (2020). Images and Videos from Owens Lake and Badwater Basin in central California, taken in 2016 and 2018 [Data set]. PANGAEA - Data Publisher for Earth &amp; Environmental Science. https://doi.org/10.1594/PANGAEA.911054 (4) Lasser, J., Karius, V. (2020). Chemical characterization of salt samples from Owens Lake and Badwater Basin, central California, collected in 2016 and 2018. PANGAEA - Data Publisher for Earth &amp; Environmental Science. https://doi.org/10.1594/PANGAEA.911239 (5) Nield, J. M., Lasser, J., Goehring, L. (2020). TLS surface scans from Owens Lake and Badwater Basin, central California, measured in 2016 and 2018 [Data set]. PANGAEA - Data Publisher for Earth &amp; Environmental Science. https://doi.org/10.1594/PANGAEA.911233 (6) Nield, J. M., Lasser, J., Goehring, L. (2020): Temperature and humidity time-series from Owens Lake, central California, measured during one week in November 2016 (Version 2). Max Planck Institute for Dynamics and Self-Organization, PANGAEA, https://doi.org/10.1594/PANGAEA.922231</span
Analysis of single-crystal neutron diffuse scattering from ice Ih
No full textThe single-crystal neutron diffuse scattering from ice contains a great deal of information, not only on the disorder of the hydrogen atoms but also on the instantaneous atomic positions. It is difficult to extract this information, and a series of reverse Monte Carlo (RMC) techniques have been developed for this purpose, with mixed success. The present paper presents new constrained RMC methods used to try and obtain more reliable information on the static and thermal disorder in ice. However it has been found that the RMC results depend strongly on the starting configuration, meaning that some of the conclusions of the earlier paper of Nield and Whitworth (Nield, V. M.; Whitworth, R. W. J. Phys.: Condens. Matter 1995, 7, 8258) are invalid
Letter to Nature. Iron deficiency induces the formation of an antenna ring around trimeric photosystem I in cyanobacteria.
No full textAlthough iron is the fourth most abundant element in the Earth's crust, its concentration in the aquatic ecosystems-particularly the open oceans-is sufficiently low to limit photosynthetic activity and phytoplankton growth. Cyanobacteria, a major class of phytoplankton, respond to iron deficiency by expressing the 'iron-stress-induced' gene, isiA(ref. 3). The protein encoded by this gene has an amino-acid sequence that shows significant homology with one of the chlorophyll a-binding proteins (CP43) of photosystem II (PSII). The precise function of the CP43-like protein, here called CP43', has not been elucidated, although there have been many suggestions. Here we show that CP43' associates with photosystem I (PSI) to form a complex that consists of a ring of 18 CP43' molecules around a PSI trimer. This significantly increases the size of the light-harvesting system of PSI. The utilization of a PSII-like protein as an extra antenna for PSI emphasises the flexibility of cyanobacterial light-harvesting systems, and seems to be a strategy which compensates for the lowering of phycobilisome and PSI levels in response to iron deficienc
Iron-stress induces the formation of an antenna ring around trimeric PSI in cyanobacteria
No full text[Report to Chief J. E. Curry, by an unknown author #1]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
[Report to Chief J. E. Curry, by an unknown author #2]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
Surface and subsurface characterisation of salt pans expressing polygonal patterns
No full textThe data set described here contains information about the surface, subsurface and environmental conditions of salt pans that express polygonal patterns in their surface salt crust (Lasser et al., 2020b), DOI: 10.5880/fidgeo.2020.037. Information stems from 5 field sites at Badwater Basin and 21 field sites at Owens Lake – both in central California. All data was recorded during two field campaigns, from between November and December, 2016, and in January 2018. Crust surfaces, including the mean diameter and fluctuations in the height of the polygonal patterns, were characterised by terrestrial laser scanner. The data contains the resulting three dimensional point clouds, which describe these surfaces. The subsurface is characterised by grain size distributions of samples taken from depths between 5 cm and 100 cm below the salt crust, and measured with a laser particle size analyser. Subsurface salinity profiles were recorded and the ground water density was also measured. Additionally, the salts present in the crust and pore water were analysed to determine their compo- sition. To characterise the environmental conditions at Owens Lake, including the differences between nearby crust features, records were made of the temperature and relative humidity during one week in November 2016. The field sites are characterised by images, showing the general context of each site, such as pictures of selected salt polygons, including any which were sampled, a typical core from each site at which core samples were taken and close-ups of the salt crust morphology. Finally, two videos of salt crust growth over the course of spring 2018 and reconstructed from time-lapse images are included
Oxyphotobacteria: antenna ring around photosystem I
No full textThe oceanic picoplankton Prochlorococcus - probably the most abundant photosynthetic organism on our planet - can grow at great depths where light intensity is very low. We have found that the chlorophyll-binding proteins in a deep-living strain of this oxyphotobacterium form a ring around a trimer of the photosystem I (PS I) photosynthetic reaction centre, a clever arrangement that maximizes the capture of light energy in such dim conditions
Structural analysis of the photosystem I supercomplex of cyanobacteria induced by iron deficiency.
No full textHere we describe the three-dimensional structure of the newly discovered CP43'-photosystem I (PSI) supercomplex of cyanobacteria calculated by single-particle analysis of images obtained by electron cryomicroscopy (cryo-EM). This large membrane protein complex has a molecular mass of approximately 2 MDa and is found in cyanobacteria when grown in iron deficient media. It is composed of a reaction center trimer surrounded by 18 subunits of the chlorophyll a binding CP43'protein, encoded by the isiA gene, which increases the light harvesting capacity of PSI by approximately 70%. By modeling higher-resolution structural data obtained from X-ray crystallography into the three-dimensional (3D) cryo-EM map, we have been able to gain a better understanding of the structure and functional properties of this supermolecular complex. We have identified three separate clusters of chlorophyll molecules at the periphery of the PSI core which may aid energy transfer from the CP43' antenna ring to the reaction center. Moreover, it is shown that despite the replacement of ferredoxin with flavodoxin as an electron acceptor under iron stress conditions, the 3D map has density to accommodate the extrinsic proteins, PsaC, PsaD, and PsaE. The presence of these three proteins was also confirmed by immunoblottin
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