Pseudoreversion substitution at large-subunit residue 54 influences the CO2/O2 specificity of chloroplast ribulose-bisphosphate carboxylase/oxygenase. 1995

R J Spreitzer, and G Thow, and G Zhu
Department of Biochemistry, University of Nebraska, Lincoln 68588-0664, USA.

Chlamydomonas reinhardtii mutant 31-4E lacks ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco; EC 4.1.1.39) holoenzyme due to a mutation in the chloroplast rbcL gene. This mutation causes a glycine54-to-aspartate substitution within the N-terminal domain of the Rubisco large subunit. In the present study, photosynthesis-competent revertants were selected to determine whether other amino acid substitutions might complement the primary defect. Revertants were found to arise from only true reversion or either of two forms of pseudoreversion affecting residue 54. One pseudorevertant has a glycine54-to-alanine substitution that decreases the accumulation of holoenzyme, but the purified Rubisco has near-normal kinetic properties. The other pseudorevertant has a glycine54-to-valine substitution that causes an even greater decrease in holoenzyme accumulation. Rubisco purified from this strain was found to have an 83% decrease in the Vmax of carboxylation and an 18% decrease in the CO2/O2 specificity factor. These results indicate that small increases in the size of amino acid side chains can influence Rubisco assembly or stability. Even though such changes occur far from the active site, they also play a significant role in determining Rubisco catalytic efficiency.

UI MeSH Term Description Entries
D007700 Kinetics The rate dynamics in chemical or physical systems.
D010100 Oxygen An element with atomic symbol O, atomic number 8, and atomic weight [15.99903; 15.99977]. It is the most abundant element on earth and essential for respiration. Dioxygen,Oxygen-16,Oxygen 16
D011994 Recombinant Proteins Proteins prepared by recombinant DNA technology. Biosynthetic Protein,Biosynthetic Proteins,DNA Recombinant Proteins,Recombinant Protein,Proteins, Biosynthetic,Proteins, Recombinant DNA,DNA Proteins, Recombinant,Protein, Biosynthetic,Protein, Recombinant,Proteins, DNA Recombinant,Proteins, Recombinant,Recombinant DNA Proteins,Recombinant Proteins, DNA
D002245 Carbon Dioxide A colorless, odorless gas that can be formed by the body and is necessary for the respiration cycle of plants and animals. Carbonic Anhydride,Anhydride, Carbonic,Dioxide, Carbon
D002736 Chloroplasts Plant cell inclusion bodies that contain the photosynthetic pigment CHLOROPHYLL, which is associated with the membrane of THYLAKOIDS. Chloroplasts occur in cells of leaves and young stems of plants. They are also found in some forms of PHYTOPLANKTON such as HAPTOPHYTA; DINOFLAGELLATES; DIATOMS; and CRYPTOPHYTA. Chloroplast,Etioplasts,Etioplast
D003001 Cloning, Molecular The insertion of recombinant DNA molecules from prokaryotic and/or eukaryotic sources into a replicating vehicle, such as a plasmid or virus vector, and the introduction of the resultant hybrid molecules into recipient cells without altering the viability of those cells. Molecular Cloning
D005998 Glycine A non-essential amino acid. It is found primarily in gelatin and silk fibroin and used therapeutically as a nutrient. It is also a fast inhibitory neurotransmitter. Aminoacetic Acid,Glycine, Monopotassium Salt,Glycine Carbonate (1:1), Monosodium Salt,Glycine Carbonate (2:1), Monolithium Salt,Glycine Carbonate (2:1), Monopotassium Salt,Glycine Carbonate (2:1), Monosodium Salt,Glycine Hydrochloride,Glycine Hydrochloride (2:1),Glycine Phosphate,Glycine Phosphate (1:1),Glycine Sulfate (3:1),Glycine, Calcium Salt,Glycine, Calcium Salt (2:1),Glycine, Cobalt Salt,Glycine, Copper Salt,Glycine, Monoammonium Salt,Glycine, Monosodium Salt,Glycine, Sodium Hydrogen Carbonate,Acid, Aminoacetic,Calcium Salt Glycine,Cobalt Salt Glycine,Copper Salt Glycine,Hydrochloride, Glycine,Monoammonium Salt Glycine,Monopotassium Salt Glycine,Monosodium Salt Glycine,Phosphate, Glycine,Salt Glycine, Monoammonium,Salt Glycine, Monopotassium,Salt Glycine, Monosodium
D000595 Amino Acid Sequence The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION. Protein Structure, Primary,Amino Acid Sequences,Sequence, Amino Acid,Sequences, Amino Acid,Primary Protein Structure,Primary Protein Structures,Protein Structures, Primary,Structure, Primary Protein,Structures, Primary Protein
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D001483 Base Sequence The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence. DNA Sequence,Nucleotide Sequence,RNA Sequence,DNA Sequences,Base Sequences,Nucleotide Sequences,RNA Sequences,Sequence, Base,Sequence, DNA,Sequence, Nucleotide,Sequence, RNA,Sequences, Base,Sequences, DNA,Sequences, Nucleotide,Sequences, RNA

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