Formation of the active site of ribulose-1,5-bisphosphate carboxylase/oxygenase by a disorder-order transition from the unactivated to the activated form

Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCo) catalyzes the key first step in photosynthetic CO2 fixation, the reaction that incorporates CO2 into sugar. In this study, refined crystal structures of unactivated tobacco RuBisCo and activated RuBisCo from spinach and tobacco, in complex wi...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1993-11, Vol.90 (21), p.9968-9972
Main Authors: Schreuder, H.A, Knight, S, Curmi, P.M.G, Andersson, I, Cascio, D, Branden, C.I, Eisenberg, D
Format: Article
Language:English
Subjects:
Active sites
Amino Acid Sequence
Analytical, structural and metabolic biochemistry
ANATOMIA DE LA PLANTA
ANATOMIE VEGETALE
Atoms
Binding Sites
Biochemistry
Biological and medical sciences
Catalysis
Crystal structure
Enzyme Activation
Enzymes
Enzymes and enzyme inhibitors
FOTOSINTESIS
Fundamental and applied biological sciences. Psychology
Lyases
Macromolecular Substances
MINERALOGIA
MINERALOGIE
Molecular Sequence Data
Molecules
NICOTIANA
Nicotiana - enzymology
Phosphates
PHOTOSYNTHESE
Plants - enzymology
Plants, Toxic
Protein Structure, Secondary
PROTEINAS VEGETALES
PROTEINE VEGETALE
Proteins
RAYON X
RAYOS-X
RIBULOSA-BIFOSFATO CARBOXILASA
RIBULOSE-BISPHOSPHATE CARBOXYLASE
Ribulose-Bisphosphate Carboxylase - chemistry
Ribulose-Bisphosphate Carboxylase - metabolism
Spinach
SPINACIA OLERACEA
Tobacco
Vegetables
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Summary:Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCo) catalyzes the key first step in photosynthetic CO2 fixation, the reaction that incorporates CO2 into sugar. In this study, refined crystal structures of unactivated tobacco RuBisCo and activated RuBisCo from spinach and tobacco, in complex with the reaction-intermediate analog 2-carboxyarabinitol 1,5-bisphosphate (CABP), are compared. Both plant enzymes are hexadecameric complexes of eight large and eight small subunits with a total relative molecular mass of approximately 550,000. The comparison of activated and unactivated forms of RuBisCo provides insight into the dynamics of action of this enzyme. The catalytic site, which is open to the solvent in the unactivated enzyme, becomes shielded in the activated CABP complex. This shielding is accomplished by a 12-angstrom movement of the active-site "loop 6" (residues 331-338) and a disorder-order transition of three loops near the active-site entrance, the N terminus, the C terminus, and a loop comprising residues 64-68. All these residues belong to the catalytic large subunit. Domain rotations of about 2 degrees are observed, also tightening the active-site cleft. These observations provide an explanation for the extremely tight binding (Kd less than or equal to 10(-11) M) of the CABP molecule. A striking correlation exists between crystallographic temperature factors in the activated enzyme and the magnitude of the atomic movement upon activation
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.90.21.9968