4MKV

Structure of Pisum sativum Rubisco with ABA

Summary for 4MKV

• Entry DOI: 10.2210/pdb4mkv/pdb
• Descriptor: Ribulose bisphosphate carboxylase large chain, Ribulose bisphosphate carboxylase small chain 3A, chloroplastic, RIBULOSE-1,5-DIPHOSPHATE, ... (6 entities in total)
• Functional Keywords: rubisco, ribulose-1, 5-bisphosphate, garden pea, abscisic acid, lyase
• Biological source: Pisum sativum (garden pea); More
• Total number of polymer chains: 8
• Total formula weight: 264024.91

Authors

Loewen, M.C.,Loewen, P.C.,Switala, J. (deposition date: 2013-09-05, release date: 2013-10-16, Last modification date: 2024-11-06)

Primary citation

Galka, M.M.,Rajagopalan, N.,Buhrow, L.M.,Nelson, K.M.,Switala, J.,Cutler, A.J.,Palmer, D.R.,Loewen, P.C.,Abrams, S.R.,Loewen, M.C.
Identification of Interactions between Abscisic Acid and Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase.
Plos One, 10:e0133033-e0133033, 2015

PubMed Abstract: Abscisic acid ((+)-ABA) is a phytohormone involved in the modulation of developmental processes and stress responses in plants. A chemical proteomics approach using an ABA mimetic probe was combined with in vitro assays, isothermal titration calorimetry (ITC), x-ray crystallography and in silico modelling to identify putative (+)-ABA binding-proteins in crude extracts of Arabidopsis thaliana. Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) was identified as a putative ABA-binding protein. Radiolabelled-binding assays yielded a Kd of 47 nM for (+)-ABA binding to spinach Rubisco, which was validated by ITC, and found to be similar to reported and experimentally derived values for the native ribulose-1,5-bisphosphate (RuBP) substrate. Functionally, (+)-ABA caused only weak inhibition of Rubisco catalytic activity (Ki of 2.1 mM), but more potent inhibition of Rubisco activation (Ki of ~ 130 μM). Comparative structural analysis of Rubisco in the presence of (+)-ABA with RuBP in the active site revealed only a putative low occupancy (+)-ABA binding site on the surface of the large subunit at a location distal from the active site. However, subtle distortions in electron density in the binding pocket and in silico docking support the possibility of a higher affinity (+)-ABA binding site in the RuBP binding pocket. Overall we conclude that (+)-ABA interacts with Rubisco. While the low occupancy (+)-ABA binding site and weak non-competitive inhibition of catalysis may not be relevant, the high affinity site may allow ABA to act as a negative effector of Rubisco activation.

PubMed: 26197050
DOI: 10.1371/journal.pone.0133033

Experimental method

X-RAY DIFFRACTION (2.15 Å)