Downregulation of Rubisco Activity by Non-enzymatic Acetylation of RbcL

Abstract

Atmospheric carbon dioxide (CO2) is assimilated by the most abundant but sluggish enzyme, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). Here we show that acetylation of lysine residues of the Rubisco large subunit (RbcL), including Lys201 and Lys334 in the active sites, may be an important mechanism in the regulation of Rubisco activities. It is well known that Lys201 reacts with CO2 for carbamylation, a prerequisite for both carboxylase and oxygenase activities of Rubisco, and Lys334 contacts with ribulose-1,5-bisphosphate (RuBP). The acetylation level of RbcL in plants is lower during the day and higher at night, inversely correlating with the Rubisco carboxylation activity. A search of the chloroplast proteome database did not reveal a canonical acetyltransferase; instead, we found that a plant-derived metabolite, 7-acetoxy-4-methylcoumarin (AMC), can non-enzymatically acetylate both native Rubisco and synthesized RbcL peptides spanning Lys334 or Lys201. Furthermore, lysine residues were modified by synthesized 4-methylumbelliferone esters with different electro- and stereo-substitutes, resulting in varied Rubisco activities. 1-Chloroethyl 4-methylcoumarin-7-yl carbonate (ClMC) could transfer the chloroethyl carbamate group to lysine residues of RbcL and completely inactivate Rubisco, whereas bis(4-methylcoumarin-7-yl) carbonate (BMC) improved Rubisco activity through increasing the level of Lys201 carbamylation. Our findings indicate that RbcL acetylation negatively regulates Rubisco activity, and metabolic derivatives can be designed to dissect and improve CO2 fixation efficiency of plants through lysine modification.

Proteome-wide profiling of protein lysine acetylation in Aspergillus flavus

“…Hence, determination of which protein acetyltransferases modify these various proteins remains to be investigated in future studies. In addition to the enzyme-catalyzed acetylation, nonenzymatic acetylation can also result in lysine modification [50], which plays different roles according to different species [51,52]. In E .…”

First comprehensive proteome analysis of lysine crotonylation in seedling leaves of Nicotiana tabacum

“…For example, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), the key carbon fixation enzyme, was crotonylated at 15 amino acid sites. The key amino acid residues of Rubisco, K201 and K334 which were identified as acetylated resulting in the downregulation of Rubisco activity 47 , also modified through crotonylation. This result suggested that crotonylation might change Rubisco activity in coordination with acetylation.…”

The Impacts of Fluctuating Light on Crop Performance

“…While the effects of phosphorylation on Rca activity are not known yet, this suggests a potential method of regulation for carbon reduction enzymes in addition to the thioredoxin-mediated regulation discussed above. Other posttranslational regulatory mechanisms directly affect Rubisco (Houtz et al, 2008), such as acetylation (Gao et al, 2016), but their effects in dynamic light have yet to be examined. As more of the key players are identified and the mechanisms by which they regulate carbon metabolism in rapidly changing light conditions are elucidated, they will likely be used to enhance the responsiveness of carbon reduction enzymes in fluctuating light.…”