title: Sliding-layer conformational change limited by the quaternary structure of plant RuBisCO.
abstract: RuBisCO, D-ribulose-1,5-bisphosphate carboxylase-oxygenase (EC 4.1.1.39), converts carbon dioxide to sugar in the first step of photosynthesis. In plants and some bacteria, this enzyme has an L8S8 structure, where L is the large catalytic subunit and S is the small subunit of unknown function. The molecule resembles a keg 105 A along the 4-fold axis and 132 A in diameter at the widest point of the keg. Here we describe the quaternary structure of RuBisCO from N. tabacum, the first L8S8 type known from an X-ray crystallographic study at near-atomic resolution (3 A). The structure shows that all eight L subunits are elongated along the 4-fold axis so that the molecule cannot be simply described as layers of subunits, as it had been from studies by electron microscopy. The structure, with its elongated and interdigitated L subunits, is evidence against a large, sliding-layer conformational change in plant RuBisCO, as proposed recently in Nature for the same enzyme from Alcaligenes eutrophus.
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D003460:Crystallization; D046911:Macromolecular Substances; D010944:Plants / Q000201:enzymology*; D010947:Plants, Toxic; D011487:Protein Conformation; D012273:Ribulose-Bisphosphate Carboxylase; D014026:Nicotiana / Q000201:enzymology; D014961:X-Ray Diffraction
chemical_list: D046911:Macromolecular Substances; D012273:Ribulose-Bisphosphate Carboxylase