Deletion of nine carboxy-terminal residues of the Rubisco small subunit decreases thermal stability but does not eliminate function.
A recent X-ray crystal structure of ribulose-1,5-bisphosphate carboxylase/oxygenase from the green alga Chlamydomonas reinhardtii lacks 13 carboxy-terminal residues of the small subunit. To determine the importance of this divergent region, a non-sense mutation was created that removes nine residues. This engineered gene was transformed into a Chlamydomonas strain that lacks the small-subunit gene family. The resulting holoenzyme has a normal CO(2)/O(2) specificity but decreased carboxylation V(max). Whereas wild-type enzyme retained most of its carboxylase activity after a 10-min incubation at 55 degrees C, the mutant enzyme was inactivated. Thus, although disordered or divergent, the carboxy terminus is required for maximal activity and stability.
Esquível
Maria G
MG
Department of Botany and Biological Engineering, Technical University of Lisbon, P-1399 Lisbon, Portugal.
Anwaruzzaman
M
M
Spreitzer
Robert J
RJ
D000595:Amino Acid Sequence; D000818:Animals; D002384:Catalysis; D016825:Chlamydomonas reinhardtii / Q000201:enzymology*; D004591:Electrophoresis, Polyacrylamide Gel; D004795:Enzyme Stability; D015151:Immunoblotting; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D012273:Ribulose-Bisphosphate Carboxylase / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D013696:Temperature
D012273:Ribulose-Bisphosphate Carboxylase