Post-translational Modifications in Regulation of Chloroplast Function: Recent Advances

Grabsztunowicz, Magda; Koskela, Minna M.; Mulo, Paula

doi:10.3389/fpls.2017.00240

Cited by 65 publications

(37 citation statements)

References 156 publications

(221 reference statements)

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“…Additionally, we suggest it may be possible that the RbcL:RbcS ratio could be dynamically regulated with impacts on both enzyme activity and the binding position of RbcS. Moreover, rubisco undergoes numerous posttranslational modifications that regulate its activity and subunit interactions (reviewed in Grabsztunowicz et al, 2017). In plants, phosphorylation influences rubisco kinetics (Lohrig et al, 2009) and modulate the interactions between RbcL, RbcS, and rubisco activase (Guitton and Mache, 1987;Aggarwal et al, 1993).…”

Section: Discussionmentioning

confidence: 99%

Binding Options for the Small Subunit-Like Domain of Cyanobacteria to Rubisco

2020

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Citation:Rohnke BA, Kerfeld CA and Montgomery BL (2020) Binding Options for the Small Subunit-Like Domain of Cyanobacteria to Rubisco.Two proteins found in cyanobacteria contain a C-terminal domain with homology to the small subunit of rubisco (RbcS). These small subunit-like domains (SSLDs) are important features of CcmM, a protein involved in the biogenesis of carboxysomes found in all β-cyanobacteria, and a rubisco activase homolog [activase-like protein of cyanobacteria (ALC)] found in over a third of sequenced cyanobacterial genomes. Interaction with rubisco is crucial to the function of CcmM and is believed to be important to ALC as well. In both cases, the SSLD aggregates rubisco, and this nucleation event may be important in regulating rubisco assembly and activity. Recently, two independent studies supported the conclusion that the SSLD of CcmM binds equatorially to L 8 S 8 holoenzymes of rubisco rather than by displacing an RbcS, as its structural homology would suggest. We use sequence analysis and homology modeling to examine whether the SSLD from the ALC could bind the large subunit of rubisco either via an equatorial interaction or in an RbcS site, if available. We suggest that the SSLD from the ALC of Fremyella diplosiphon could bind either in a vacant RbcS site or equatorially. Our homology modeling takes into account N-terminal residues not represented in available cryo-electron microscopy structures that potentially contribute to the interface between the large subunit of rubisco (RbcL) and RbcS. Here, we suggest the perspective that binding site variability as a means of regulation is plausible and that the dynamic interaction between the RbcL, RbcS, and SSLDs may be important for carboxysome assembly and function.

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Section: Discussionmentioning

confidence: 99%

Binding Options for the Small Subunit-Like Domain of Cyanobacteria to Rubisco

2020

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“…Similarly, proteins with both reversible cysteine oxidation and phosphorylation sites are largely recognized [13] , [14] , yet studies identifying proteoforms simultaneously affected by these modifications are sparse [15] , [16] . Discovery and targeted validation of these PTMs and the effect on protein structure and function are particularly lacking for photosynthetic organisms and must be advanced to begin meaningful definition of signaling pathways [17] .…”

Section: Introductionmentioning

confidence: 99%

The phosphorylated redox proteome of Chlamydomonas reinhardtii: Revealing novel means for regulation of protein structure and function

2018

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Post-translational modifications (PTMs) are covalent modifications to protein residues which may alter both conformation and activity, thereby modulating signaling and metabolic processes. While PTMs have been largely investigated independently, examination into how different modification interact, or crosstalk, will reveal a more complete understanding of the reciprocity of signaling cascades across numerous pathways. Combinatorial reversible thiol oxidation and phosphorylation in eukaryotes is largely recognized, but rigorous approaches for experimental discovery are underdeveloped. To begin meaningful interrogation of PTM crosstalk in systems biology research, knowledge of targeted proteins must be advanced. Herein, we demonstrate protein-level enrichment of reversibly oxidized proteoforms in Chlamydomonas reinhardtii with subsequent phosphopeptide analysis to determine the extent of phosphorylation in the redox thiol proteome. Label-free quantification was used to quantify 3353 oxidized Cys-sites on 1457 enriched proteins, where sequential phosphopeptide enrichment measured 1094 sites of phosphorylation on 720 proteins with 23% (172 proteins) also identified as reversibly oxidized. Proteins identified with both reversible oxidation and phosphorylation were involved in signaling transduction, ribosome and translation-related machinery, and metabolic pathways. Several redox-modified Calvin-Benson cycle proteins were found phosphorylated and many kinases/phosphatases involved in phosphorylation-dependent photosynthetic state transition and stress-response pathways had sites of reversible oxidation. Identification of redox proteins serves as a crucial element in understanding stress response in photosynthetic organisms and beyond, whereby knowing the ensemble of modifications co-occurring with oxidation highlights novel mechanisms for cellular control.

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“…The detected increase in the effective quantum yield, as shown in Fig. 3D , could be due to regulation of LHCX proteins at the posttranslational level ( 22 , 32 , 33 ) or carried out by other relevant gene products. We note that a total of 55 genes representing most of the genes involved in photosynthesis-related GO terms were up-regulated in the eGFP transformants under high-intensity light conditions (fig.…”

Section: Resultsmentioning

confidence: 92%