Structure of green-type Rubisco activase from tobacco

• Published in: Nature structural & molecular biology Vol. 18; no. 12; pp. 1366 - 1370
• Main Authors: Stotz, Mathias, Mueller-Cajar, Oliver, Ciniawsky, Susanne, Wendler, Petra, Hartl, F Ulrich, Bracher, Andreas, Hayer-Hartl, Manajit
• Format: Journal Article
• Language: English
• Published: New York Nature Publishing Group US 01.12.2011; Nature Publishing Group
• Subjects: 631/337/470; 631/45/535; 631/45/607; Adenosine triphosphatase; Amino Acid Sequence; ATP; Biochemistry; Biological Microscopy; Biomedical and Life Sciences; Carbon dioxide fixation; Crystal structure; Crystallography, X-Ray; Electron microscopy; Enzymes; Genetic aspects; Inactivation; Life Sciences; Membrane Biology; Models, Molecular; Molecular Sequence Data; Molecular structure; Nicotiana - enzymology; Nicotiana - metabolism; Phosphates; Photosynthesis; Photosynthesis - physiology; Physiological aspects; Plant Proteins - chemistry; Plant Proteins - physiology; Protein Structure; Protein Structure, Tertiary; Ribulose-Bisphosphate Carboxylase - metabolism; Rubisco; Sequence Alignment; Sugar; Tissue Plasminogen Activator - chemistry; Tissue Plasminogen Activator - physiology; Tobacco; Tobacco (Plant); Germany
• ISSN: 1545-9993; 1545-9985; 1545-9985
• DOI: 10.1038/nsmb.2171

The enzyme Rubisco has a central role in atmospheric CO 2 fixation. Rubisco can be inactivated if its sugar substrate is bound prior to carbamylation of a residue in the active site. The structure of tobacco Rca, the enzyme that removes the bound sugar substrate and activates Rubisco, is now presented, offering insight into this process. Rubisco, the enzyme that catalyzes the fixation of atmospheric CO 2 in photosynthesis, is subject to inactivation by inhibitory sugar phosphates. Here we report the 2.95-Å crystal structure of Nicotiana tabacum Rubisco activase (Rca), the enzyme that facilitates the removal of these inhibitors. Rca from tobacco has a classical AAA + -protein domain architecture. Although Rca populates a range of oligomeric states when in solution, it forms a helical arrangement with six subunits per turn when in the crystal. However, negative-stain electron microscopy of the active mutant R294V suggests that Rca functions as a hexamer. The residues determining species specificity for Rubisco are located in a helical insertion of the C-terminal domain and probably function in conjunction with the N-domain in Rubisco recognition. Loop segments exposed toward the central pore of the hexamer are required for the ATP-dependent remodeling of Rubisco, resulting in the release of inhibitory sugar.