1ir2
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Crystal Structure of Activated Ribulose-1,5-bisphosphate Carboxylase/oxygenase (Rubisco) from Green alga, Chlamydomonas reinhardtii Complexed with 2-Carboxyarabinitol-1,5-bisphosphate (2-CABP)
OverviewOverview
Ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) catalyzes the, initial steps of photosynthetic carbon reduction and photorespiratory, carbon oxidation cycles by combining CO(2) and O(2), respectively, with, ribulose-1,5-bisphosphate. Many photosynthetic organisms have form I, rubiscos comprised of eight large (L) and eight small (S) subunits. The, crystal structure of the complex of activated rubisco from the green alga, Chlamydomonas reinhardtii and the reaction intermediate analogue, 2-carboxyarabinitol-1,5-bisphosphate (2-CABP) has been solved at 1.84 A, resolution (R(cryst) of 15.2 % and R(free) of 18.1 %). The subunit, arrangement of Chlamydomonas rubisco is the same as those of the, previously solved form I rubiscos. Especially, the present structure is, very similar to the activated spinach structure complexed with 2-CABP in, the L-subunit folding and active-site conformation, but differs in, S-subunit folding. The central insertion of the Chlamydomonas S-subunit, forms the longer betaA-betaB loop that protrudes deeper into the solvent, channel of rubisco than higher plant, cyanobacterial, and red algal, (red-like) betaA-betaB loops. The C-terminal extension of the, Chlamydomonas S-subunit does not protrude into the solvent channel, unlike, that of the red algal S-subunit, but lies on the protein surface anchored, by interactions with the N-terminal region of the S-subunit. Further, the, present high-resolution structure has revealed novel post-translational, modifications. Residue 1 of the S-subunit is N(alpha)-methylmethionine, residues 104 and 151 of the L-subunit are 4-hydroxyproline, and residues, 256 and 369 of the L-subunit are S(gamma)-methylcysteine. Furthermore, the, unusual electron density of residue 471 of the L-subunit, which has been, deduced to be threonine from the genomic DNA sequence, suggests that the, residue is isoleucine produced by RNA editing or O(gamma)-methylthreonine.
About this StructureAbout this Structure
1IR2 is a Protein complex structure of sequences from Chlamydomonas reinhardtii with MG, CAP and GOL as ligands. Active as Ribulose-bisphosphate carboxylase, with EC number 4.1.1.39 Full crystallographic information is available from OCA.
ReferenceReference
Crystal structure of activated ribulose-1,5-bisphosphate carboxylase/oxygenase from green alga Chlamydomonas reinhardtii complexed with 2-carboxyarabinitol-1,5-bisphosphate., Mizohata E, Matsumura H, Okano Y, Kumei M, Takuma H, Onodera J, Kato K, Shibata N, Inoue T, Yokota A, Kai Y, J Mol Biol. 2002 Feb 22;316(3):679-91. PMID:11866526
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