Download MendeleyStructure-function studies with the unique hexameric form II ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) from Rhodopseudomonas palustris.
Satagopan, S., Chan, S., Perry, L.J., Tabita, F.R.(2014) J Biol Chem 289: 21433-21450
- PubMed: 24942737
- DOI: https://doi.org/10.1074/jbc.M114.578625
- Primary Citation of Related Structures:
4LF1, 4LF2 - PubMed Abstract:
The first x-ray crystal structure has been solved for an activated transition-state analog-bound form II ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). This enzyme, from Rhodopseudomonas palustris, assembles as a unique hexamer with three pairs of catalytic large subunit homodimers around a central 3-fold symmetry axis. This oligomer arrangement is unique among all known Rubisco structures, including the form II homolog from Rhodospirillum rubrum. The presence of a transition-state analog in the active site locked the activated enzyme in a "closed" conformation and revealed the positions of critical active site residues during catalysis. Functional roles of two form II-specific residues (Ile(165) and Met(331)) near the active site were examined via site-directed mutagenesis. Substitutions at these residues affect function but not the ability of the enzyme to assemble. Random mutagenesis and suppressor selection in a Rubisco deletion strain of Rhodobacter capsulatus identified a residue in the amino terminus of one subunit (Ala(47)) that compensated for a negative change near the active site of a neighboring subunit. In addition, substitution of the native carboxyl-terminal sequence with the last few dissimilar residues from the related R. rubrum homolog increased the enzyme's kcat for carboxylation. However, replacement of a longer carboxyl-terminal sequence with termini from either a form III or a form I enzyme, which varied both in length and sequence, resulted in complete loss of function. From these studies, it is evident that a number of subtle interactions near the active site and the carboxyl terminus account for functional differences between the different forms of Rubiscos found in nature.
Organizational Affiliation:
From the Department of Microbiology, The Ohio State University, Columbus, Ohio 43210-1292 and.
