Structural highlights
Function[RCA1_TOBAC] Activation of RuBisCO (ribulose-1,5-bisphosphate carboxylase/oxygenase; EC 4.1.1.39) involves the ATP-dependent carboxylation of the epsilon-amino group of lysine leading to a carbamate structure. Publication Abstract from PubMedRubisco, 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-A 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. Structure of green-type Rubisco activase from tobacco.,Stotz M, Mueller-Cajar O, Ciniawsky S, Wendler P, Hartl FU, Bracher A, Hayer-Hartl M Nat Struct Mol Biol. 2011 Nov 6. doi: 10.1038/nsmb.2171. PMID:22056769[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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