Deletion of nine carboxy-terminal residues of the Rubisco small subunit decreases thermal stability but does not eliminate function

• Published in: FEBS letters 2002-06, Vol.520 (1), p.73-76
• Main Authors: Esquı́vel, Maria G., Anwaruzzaman, M., Spreitzer, Robert J.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Catalysis; Chlamydomonas reinhardtii; Chlamydomonas reinhardtii - enzymology; Chloroplast enzyme; Electrophoresis, Polyacrylamide Gel; Enzyme Stability; Genetic engineering; Immunoblotting; K c, K m CO2; K o, K m O2; Molecular Sequence Data; Mutagenesis, Site-Directed; Mutation; Photosynthesis; Protein stability; Ribulose-1,5-bisphosphate carboxylase/oxygenase; Ribulose-Bisphosphate Carboxylase - genetics; Ribulose-Bisphosphate Carboxylase - metabolism; Rubisco, ribulose-1,5-bisphosphate carboxylase/oxygenase; RuBP, ribulose-1,5-bisphosphate; Sequence Deletion; Sequence Homology, Amino Acid; Temperature; V c, V max of carboxylation; V o, V max of oxygenation; Ω, CO2/O2 specificity factor
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/S0014-5793(02)02770-9

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°C, the mutant enzyme was inactivated. Thus, although disordered or divergent, the carboxy terminus is required for maximal activity and stability.