Agronomia

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Plant Physiology and Biochemistry 46 (2008) 275e291 www.elsevier.com/locate/plaphy

Research article

Structure and function of Rubisco
Inger Andersson a,*, Anders Backlund b
a

Department of Molecular Biology, Swedish University of Agricultural Sciences, Husargatan 3, BMC Box 590, S-751 24 Uppsala, Sweden b Division of Pharmacognosy,Department of Medicinal Chemistry, Uppsala University, BMC Box 574, S-751 23 Uppsala, Sweden Received 20 December 2007 Available online 12 January 2008

Abstract Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is the major enzyme assimilating CO2 into the biosphere. At the same time Rubisco is an extremely inefficient catalyst and its carboxylase activity is compromised by an opposing oxygenaseactivity involving atmospheric O2. The shortcomings of Rubisco have implications for crop yield, nitrogen and water usage, and for the global carbon cycle. Numerous high-resolution crystal structures of different forms of Rubisco are now available, including structures of mutant enzymes. This review uses the information provided in these structures in a structure-based sequence alignment anddiscusses Rubisco function in the context of structural variations at all levels e amino acid sequence, fold, tertiary and quaternary structure e with an evolutionary perspective and an emphasis on the structural features of the enzyme that may determine its function as a carboxylase. Ó 2008 Elsevier Masson SAS. All rights reserved.
Keywords: Rubisco; Structure-function studies; CO2/O2 specificity;Evolution; Structure-based alignment

1. Introduction Life on earth is almost exclusively dependent on the ability of photosynthetic organisms to sequester inorganic CO2 of the atmosphere into organic carbon of the biosphere via the Calvin-Benson-Bassham pathway. The primary photosynthetic CO2 reduction reaction, the binding of CO2 to the acceptormolecule ribulose-1,5-bisphosphate (RuBP) to formtwo molecules of 3-phosphoglycerate, is catalysed by the enzyme RuBP carboxylase/oxygenase (EC 4.1.1.39, Rubisco). Rubisco is found in most autotrophic organisms from prokaryotes (photosynthetic and chemoautotrophic bacteria, cyanobacteria and archaea) to eukaryotes (various algae and higher plants). It has been estimated that Rubisco can comprise up to 50% of the total soluble protein in the plantleaf or inside the microbe
Abbreviations: RuBP, ribulose-1,5-bisphosphate; Rubisco, ribulose-1,5-bisphosphate carboxylase/oxygenase; RLP, Rubisco-like protein; PDB, Protein Data Bank; L, large subunit; S, small subunit; rbcL, Rubisco large subunit gene; rbcS, Rubisco small subunit gene; 2CABP, 2-carboxyarabinitol-1,5bisphosphate. * Corresponding author. Tel.: þ46 18 471 4288; fax: þ46 18 536 971.E-mail address: inger@xray.bmc.uu.se (I. Andersson). 0981-9428/$ - see front matter Ó 2008 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.plaphy.2008.01.001

[21]. Perhaps less obvious, but as ubiquitous, is its presence in phytoplankton in the sea, which are estimated to provide more than 45% of global net primary production annually [25]. Due to the importance and abundance ofRubisco, aspects of the genetics, microbiology, molecular biology, biochemistry and evolution of the enzyme have been studied intensely. More recently, the realization of the importance of CO2 as a greenhouse gas and the occurrence of rising levels of CO2 in the Earth’s atmosphere has drawn new attention to Rubisco’s role in these processes. However, ultimately it is the unique and peculiar features ofRubisco as a catalyst that drives the continuous interest in the enzyme: Rubisco is an extremely slow catalyst and moreover its carboxylation activity is compromised by competing side-reactions, the most notable with another atmospheric gas, O2, which attacks the same enediol-intermediate of RuBP. The opposing oxygenase activity of Rubisco results in the synthesis of phosphoglycolate, a molecule...