Atomic Resolution X-ray Structure of the Substrate Recognition Domain of Higher Plant Ribulose-bisphosphate Carboxylase/Oxygenase (Rubisco) Activase

Abstract

Background: Rubisco activase has been linked to the inhibition of net photosynthesis upon warming.Results: The structure of the C-terminal domain adopts an unusually elongated shape.Conclusions: Reactivation of Rubisco may involve movement of a paddle-like extension.Significance: This work will aid in gaining a better understanding of Rubisco regulation.

Small Oligomers of Ribulose-bisphosphate Carboxylase/Oxygenase (Rubisco) Activase Are Required for Biological Activity

“…It has been speculated that this region interacts with the Rubisco enzyme via hydrophobic patches on an extended helix of Rubisco activase (26). As such, the initial association of Rubisco activase with Rubisco must be via the outside of the assembly.…”

“…The structures of the substrate recognition domain of creosote Rubisco activase (26) and an N-and C-terminally truncated tobacco Rubisco activase (1) have recently been published, showing that the enzyme has a classical AAAϩ protein domain architecture. Previous studies have shown that Rubisco activase has a high degree of polydispersity in its oligomeric forms and can form a variety of species ranging from monomers to large 660-kDa complexes, which would correspond to 16 subunits (1,(27)(28)(29)(30)(31)(32)(33).…”

The Regulatory Properties of Rubisco Activase Differ among Species and Affect Photosynthetic Induction during Light Transitions

“…3). While differences between the two polypeptides are distributed throughout the protein, residues affecting nucleotide binding are likely to fall within the AAA+ motif (Henderson et al, 2011;Stotz et al, 2011). Also, it is likely that ADP sensitivity is conferred by a residue(s) outside the Rubisco recognition domain, since Rca activity in leaf extracts of the Arabidopsis Tob-DAt (S2) transformant was inhibited by physiological ratios of ADP to ATP (Fig.…”

Regulation of Ribulose-1,5-bisphosphate Carboxylase/Oxygenase (Rubisco) Activase

“…The 1.9 Å resolution creosote bush substrate recognition domain (38) consists of a helical bundle that forms the core of the AAA ϩ C-domain and an insertion that bears the specificity residues. The 2.9 Å resolution structures of the nucleotide-free AAA ϩ modules of tobacco (32) and Arabidopsis thaliana (39) Rca demonstrate a spiral arrangement of subunits in the crystal.…”