scholarly journals Distinctive Responses of Ribulose-1,5-Bisphosphate Carboxylase and Carbonic Anhydrase in Wheat Leaves to Nitrogen Nutrition and their Possible Relationships to CO2-Transfer Resistance

1992 ◽  
Vol 100 (4) ◽  
pp. 1737-1743 ◽  
Author(s):  
Amane Makino ◽  
Hiroshi Sakashita ◽  
Jun Hidema ◽  
Tadahiko Mae ◽  
Kunihiko Ojima ◽  
...  
Keyword(s):  
Carbonic Anhydrase ◽  
Nitrogen Nutrition ◽  
Transfer Resistance ◽  
Bisphosphate Carboxylase ◽  
Wheat Leaves

Effects of Nitrogen Nutrition on Photosynthetic Functions of Wheat Leaves under Elevated Atmospheric CO2 Concentration

2010 ◽  
Vol 36 (8) ◽  
pp. 1362-1370 ◽  
Author(s):  
Xu-Cheng ZHANG ◽  
Fu-Suo ZHANG ◽  
Xian-Feng YU ◽  
Xin-Ping CHEN
Keyword(s):  
Nitrogen Nutrition ◽  
Wheat Leaves

scholarly journals Rubisco proton production can drive the elevation of CO2 within condensates and carboxysomes

2021 ◽  
Vol 118 (18) ◽  
pp. e2014406118
Author(s):  
Benedict M. Long ◽  
Britta Förster ◽  
Sacha B. Pulsford ◽  
G. Dean Price ◽  
Murray R. Badger
Keyword(s):  
Carbonic Anhydrase ◽  
Reaction Diffusion ◽  
Compartment Model ◽  
Low Light ◽  
Bisphosphate Carboxylase ◽  
Proton Production ◽  
Logical Sequence ◽  
Photosynthetic Carbon ◽  
Internal Ph ◽  
Improved Function

Membraneless organelles containing the enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) are a common feature of organisms utilizing CO2 concentrating mechanisms to enhance photosynthetic carbon acquisition. In cyanobacteria and proteobacteria, the Rubisco condensate is encapsulated in a proteinaceous shell, collectively termed a carboxysome, while some algae and hornworts have evolved Rubisco condensates known as pyrenoids. In both cases, CO2 fixation is enhanced compared with the free enzyme. Previous mathematical models have attributed the improved function of carboxysomes to the generation of elevated CO2 within the organelle via a colocalized carbonic anhydrase (CA) and inwardly diffusing HCO3−, which have accumulated in the cytoplasm via dedicated transporters. Here, we present a concept in which we consider the net of two protons produced in every Rubisco carboxylase reaction. We evaluate this in a reaction–diffusion compartment model to investigate functional advantages these protons may provide Rubisco condensates and carboxysomes, prior to the evolution of HCO3− accumulation. Our model highlights that diffusional resistance to reaction species within a condensate allows Rubisco-derived protons to drive the conversion of HCO3− to CO2 via colocalized CA, enhancing both condensate [CO2] and Rubisco rate. Protonation of Rubisco substrate (RuBP) and product (phosphoglycerate) plays an important role in modulating internal pH and CO2 generation. Application of the model to putative evolutionary ancestors, prior to contemporary cellular HCO3− accumulation, revealed photosynthetic enhancements along a logical sequence of advancements, via Rubisco condensation, to fully formed carboxysomes. Our model suggests that evolution of Rubisco condensation could be favored under low CO2 and low light environments.

Spectroscopic Examination of Protein Adsorption from Seawater onto Titanium

1993 ◽  
Vol 47 (8) ◽  
pp. 1140-1151 ◽  
Author(s):  
G. T. Taylor ◽  
P. J. Troy ◽  
M. Nullet ◽  
S. K. Sharma ◽  
B. E. Liebert ◽  
...  
Keyword(s):  
Film Thickness ◽  
Oxide Layer ◽  
Electrochemical Impedance ◽  
Surface Film ◽  
Electrochemical Techniques ◽  
Oxide Surface ◽  
State Function ◽  
Transfer Resistance ◽  
Bisphosphate Carboxylase ◽  
Oxidation Rates

Several noninvasive optical and electrochemical techniques were adapted to examine partitioning of protein from seawater onto polished titanium with the use of the plant enzyme ribulose-1,5,-bisphosphate carboxylase-oxygenase (Rubisco) as a model. Protein films, varying in surface concentrations from 0.011 to 3.606 μg cm−2, were prepared by exposing polished Ti surfaces to seawater amended with 0.04–90.80 μg mL−1 of 3H-Rubisco. Mean film thickness, d, measured by ellipsometry, increased linearly over most of the range of irreversibly bound protein (Γirr = 0.011–2.491 μg cm−2). Spatial coverages of the films were more heterogeneous at low surface coverages, indicative of heterogeneous adsorption resulting in barren Ti oxide surface sites and insular protein clusters. The thickness of the underlying Ti oxide layer, also measured by ellipsometry, was highly variable and indicated that oxidation of the surface was suppressed at high protein coverages during two-hour exposures to seawater. Vibrational spectra of surface films, from submonolayer (0.03 μg cm−2) to multilayer (3.61 μg cm−2), were obtained with the use of Fourier transform infrared reflection-absorption spectrometry (FT-IRAS). Peak areas of amide I and II bands varied linearly with Γirr, permitting noninvasive measurement of protein mass at the surface. Relative intensities of the amide II/amide I bands, band composition of the amide III, and peak frequencies varied with surface concentration, indicating unfolding of adsorbed proteins. Vibrational spectroscopic and ellipsometric evidence suggests that protein structure is most altered at low surface concentrations. Electrochemical impedance spectroscopy (EIS) performed from 100 /μHZ to 100 kHz on replicate test surfaces revealed that the electrochemical behavior of the titanium/protein interface was consistent with that of a parallel RC circuit. The charge transfer resistance, Rct, of the interface varied as a two-state function of protein concentration. The Rct increased more rapidly within the monolayer domain (0.12 to 2.8 MΩ cm2) than in the multilayer domain (2.8 to 4.9 MΩ cm2), indicating that impedance to electron flow across the interface is most influenced by protein monolayer formation and is less affected by additional layers. Estimations of rates of oxidation or dissolution of the substratum were inversely proportional to protein surface concentrations. Together these techniques provide internally consistent measurements of surface film thickness, adsorbate mass, gross chemical composition, interface organization, electrical impedance, capacitance, and oxide layer thickness. These data are useful for determining the physical state of the interface, its dynamics, and the potential oxidation rates of the substratum underlying the surface film.

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