1uzh
A CHIMERIC CHLAMYDOMONAS, SYNECHOCOCCUS RUBISCO ENZYME
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OverviewOverview
Comparison of subunit sequences and X-ray crystal structures of, ribulose-1,5-bisphosphate carboxylase/oxygenase indicates that the loop, between beta-strands A and B of the small subunit is one of the most, variable regions of the holoenzyme. In prokaryotes and nongreen algae, the, loop contains 10 residues. In land plants and green algae, the loop is, comprised of approximately 22 and 28 residues, respectively. Previous, studies indicated that the longer betaA-betaB loop was required for the, assembly of cyanobacterial small subunits with plant large subunits in, isolated chloroplasts. In the present study, chimeric small subunits were, constructed by replacing the loop of the green alga Chlamydomonas, reinhardtii with the sequences of Synechococcus or spinach. When these, engineered genes were transformed into a Chlamydomonas mutant that lacks, small-subunit genes, photosynthesis-competent colonies were recovered, indicating that loop size is not essential for holoenzyme assembly., Whereas the Synechococcus loop causes decreases in carboxylation V(max), K(m)(O(2)), and CO(2)/O(2) specificity, the spinach loop causes, complementary decreases in carboxylation V(max), K(m)(O(2)), and, K(m)(CO(2)) without a change in specificity. X-ray crystal structures of, the engineered proteins reveal remarkable similarity between the, introduced betaA-betaB loops and the respective loops in the Synechococcus, and spinach enzymes. The side chains of several large-subunit residues are, altered in regions previously shown by directed mutagenesis to influence, CO(2)/O(2) specificity. Differences in the catalytic properties of, divergent Rubisco enzymes may arise from differences in the small-subunit, betaA-betaB loop. This loop may be a worthwhile target for genetic, engineering aimed at improving photosynthetic CO(2) fixation.
About this StructureAbout this Structure
1UZH is a Protein complex structure of sequences from Chlamydomonas reinhardtii, synechococcus sp and Chlamydomonas reinhardtii with , and as ligands. Active as Ribulose-bisphosphate carboxylase, with EC number 4.1.1.39 Known structural/functional Site: . Full crystallographic information is available from OCA.
ReferenceReference
Chimeric small subunits influence catalysis without causing global conformational changes in the crystal structure of ribulose-1,5-bisphosphate carboxylase/oxygenase., Karkehabadi S, Peddi SR, Anwaruzzaman M, Taylor TC, Cederlund A, Genkov T, Andersson I, Spreitzer RJ, Biochemistry. 2005 Jul 26;44(29):9851-61. PMID:16026157
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