9CHZ

Anthoceros agrestis Rubisco assembled with Raf1 Raf2 and BSD2

Summary for 9CHZ

• Entry DOI: 10.2210/pdb9chz/pdb
• EMDB information: 45605 45607 45608 45641
• Descriptor: Rubisco large subunit, Rubisco small subunit, MAGNESIUM ION, ... (4 entities in total)
• Functional Keywords: anthoceros agrestis rubisco, photosynthesis
• Biological source: Anthoceros agrestis; More
• Total number of polymer chains: 16
• Total formula weight: 543976.86

Authors

Ang, W.S.L.,Oh, Z.G.,Li, F.W.,Gunn, L.H. (deposition date: 2024-07-02, release date: 2024-11-13, Last modification date: 2024-11-20)

Primary citation

Oh, Z.G.,Robison, T.A.,Loh, D.H.,Leong Ang, W.S.,Ng, J.,Li, F.W.,Gunn, L.H.
Unique biogenesis and kinetics of hornwort Rubiscos revealed by synthetic biology systems.
Mol Plant, 2024

PubMed Abstract: Hornworts are the only land plants that employ a pyrenoid to optimize Rubisco's CO fixation. Yet, hornwort Rubisco remains poorly characterized. Here we assemble the hornwort Anthoceros agrestis Rubisco (AaRubisco) using the Arabidopsis thaliana SynBio expression system and observed the formation of stalled intermediates, prompting us to develop a new SynBio system with A. agrestis cognate chaperones. We successfully assembled AaRubisco and Rubisco from three other hornwort species. Unlike A. thaliana Rubisco, AaRubisco assembly is not dependent on RbcX or Raf2. Kinetic characterization reveals that hornwort Rubiscos exhibit a range of catalytic rates (3-10 s), but with similar affinity (∼30 μM) and specificity (∼70) for CO. In other words, hornwort Rubiscos do not comply with the long held canonical catalytic trade-off observed in other land plants, providing experimental support that Rubisco kinetics may be phylogenetically constrained. Unexpectedly, we observed a 50% increase in AaRubisco catalytic rates when RbcX was removed from our SynBio system, without any reduction in specificity. Structural biology, biochemistry and proteomic analysis suggest that subtle differences in Rubisco large subunit interactions, when RbcX is absent during biogenesis, increases the accessibility of active sites and catalytic turnover rate. This study uncovered a previously unknown Rubisco kinetic parameter space and provides a SynBio chassis to expand the survey of other Rubisco kinetics. Our discovery could thus reshape the approaches for engineering Rubisco with superior kinetics.

PubMed: 39491367
DOI: 10.1016/j.molp.2024.10.013

Experimental method

ELECTRON MICROSCOPY (2.9 Å)