Biology subjects

Forster, B.

Publications and source records attributed to Forster, B..

3 recordsLinked to original sources

bioRxiv2023

Cyanobacterial α-carboxysome carbonic anhydrase is allosterically regulated by the Rubisco substrate RuBP

Cyanobacterial CO2 concentrating mechanisms (CCMs) sequester a globally significant proportion of carbon into the biosphere. Proteinaceous microcompartments, called carboxysomes, play a critical role in CCM function, housing two enzymes to enhance CO2 fixation: carbonic anhydrase (CA) and Rubisco. Despite its importance, our current understanding of the carboxysomal CAs found in [a]-cyanobacteria, CsoSCA, remains limited, particularly regarding the regulation of its activity. Here, we present the first structural and biochemical study of CsoSCA from the cyanobacterium Cyanobium PCC7001. Our results show that the Cyanobium CsoSCA is allosterically activated by the Rubisco substrate ribulose-1,5-bisphosphate (RuBP), and forms a hexameric trimer of dimers. Comprehensive phylogenetic and mutational analyses are consistent with this regulation appearing exclusively in cyanobacterial [a]-carboxysome CAs. These findings clarify the biologically relevant oligomeric state of -carboxysomal CAs and advance our understanding of the regulation of photosynthesis in this globally dominant lineage. One-Sentence SummaryThe carboxysomal carbonic anhydrase, CsoSCA, is allosterically activated by the Rubisco substrate RuBP, revealing a novel mechanism controlling key enzyme activity in cyanobacterial -carboxysomes.

molecular biology↗

bioRxiv2022

A cross-scale analysis to understand and quantify effects of photosynthetic enhancement on crop growth and yield

Photosynthetic manipulation provides new opportunities for enhancing crop yield. However, understanding and quantifying effectively how the seasonal growth and yield dynamics of target crops might be affected over a wide range of environments is limited. Using a state-of-the-art cross-scale model we predicted crop-level impacts of a broad list of promising photosynthesis manipulation strategies for C3 wheat and C4 sorghum. The manipulation targets have varying effects on the enzyme-limited (Ac) and electron transport-limited (Aj) rates of photosynthesis. In the top decile of seasonal outcomes, yield gains with the list of manipulations were predicted to be modest, ranging between 0 and 8%, depending on the crop type and manipulation. To achieve the higher yield gains, large increases in both Ac and Aj are needed. This could likely be achieved by stacking Rubisco function and electron transport chain enhancements or installing a full CO2 concentrating system. However, photosynthetic enhancement influences the timing and severity of water and nitrogen stress on the crop, confounding yield outcomes. Strategies enhancing Ac alone offers more consistent but smaller yield gains across environments, Aj enhancement alone offers higher gains but is undesirable in less favourable environments. Understanding and quantifying complex cross-scale interactions between photosynthesis and crop yield will challenge and stimulate photosynthesis and crop research. Summary StatementLeaf-canopy-crop prediction using a state-of-the-art cross-scale model improves understanding of how photosynthetic manipulation alters wheat and sorghum growth and yield dynamics. This generates novel insights for quantifying impacts of photosynthetic enhancement on crop yield across environments.

plant biology↗

bioRxiv2019

Structural basis for the allosteric regulation of the SbtA bicarbonate transporter by the PII-like protein, SbtB, from Cyanobium sp. PCC7001

Cyanobacteria have evolved a suite of enzymes and inorganic carbon (Ci) transporters that improve photosynthetic performance by increasing the localized concentration of CO2 around the primary CO2-fixating enzyme, Rubisco. This CO2-concentrating mechanism (CCM) is highly regulated, responds to illumination/darkness cycles and allows cyanobacteria to thrive under limiting Ci conditions. While the transcriptional control of CCM activity is well understood, less is known about how regulatory proteins might allosterically regulate Ci transporters in response to changing conditions. Cyanobacterial sodium-dependent bicarbonate transporters (SbtAs) are inhibited by PII-like regulatory proteins (SbtBs), with the inhibitory effect being modulated by adenylnucleotides. Here, we used isothermal titration calorimetry to show that SbtB from Cyanobium sp. PCC7001 (SbtB7001) binds AMP, ADP, cAMP and ATP with micromolar-range affinities. X-ray crystal structures of apo- and nucleotide-bound SbtB7001 revealed that while AMP, ADP and cAMP have little effect on the SbtB7001 structure, binding of ATP stabilizes the otherwise flexible T-loop and that the flexible C-terminal C-loop adopts several distinct conformations. We also show that ATP binding affinity is increased ten-fold in the presence of Ca2+ and we present an X-ray crystal structure of Ca2+ATP:SbtB7001 that shows how this metal ion facilitates additional stabilizing interactions with the apex of the T-loop. We propose that the Ca2+ATP-induced conformational change observed in SbtB7001 is important for allosteric regulation of SbtA activity by SbtB and is consistent with changing adenylnucleotide levels in illumination/darkness cycles.\n\nGRAPHICAL ABSTRACT\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=102 SRC=\"FIGDIR/small/762807v1_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (43K):\norg.highwire.dtl.DTLVardef@99bac2org.highwire.dtl.DTLVardef@b43082org.highwire.dtl.DTLVardef@1dcac4borg.highwire.dtl.DTLVardef@b38ea1_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗