Identification of a New Chloroplast Carbonic Anhydrase in Chlamydomonas reinhardtii1
AUTOR(ES)
Mitra, Mautusi
FONTE
American Society of Plant Biologists
RESUMO
Carbonic anhydrases (CA) are zinc-containing metalloenzymes that catalyze the reversible hydration of CO2. The three evolutionarily unrelated families of CAs are designated α-, β-, and γ-CA. Aquatic photosynthetic organisms have evolved different forms of CO2 concentrating mechanisms (CCMs) to aid Rubisco in capturing CO2 from the surrounding environment. One aspect of all CCMs is the critical roles played by various specially localized extracellular and intracellular CAs. Five CAs have previously been identified in Chlamydomonas reinhardtii, a green alga with a well-studied CCM. Here we identify a sixth gene encoding a β-type CA. This new β-CA, designated Cah6, is distinct from the two mitochondrial β-CAs in C. reinhardtii. Nucleotide sequence data show that the Cah6 cDNA contains an open reading frame encoding a polypeptide of 264 amino acids with a leader sequence likely targeting the protein to the chloroplast stroma. We have fused the Cah6 open reading frame to the coding sequence of maltose-binding protein in a pMal expression vector. The purified recombinant fusion protein is active and was used to partially characterize the Cah6 protein. The purified recombinant fusion protein was cleaved with protease Factor Xa to separate Cah6 from the maltose-binding protein and the purified Cah6 protein was used to raise an antibody. Western blots, immunolocalization studies, and northern blots collectively indicated that Cah6 is constitutively expressed in the stroma of chloroplasts. A possible role for Cah6 in the CCM of C. reinhardtii is proposed.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=429345Documentos Relacionados
- An Anaplerotic Role for Mitochondrial Carbonic Anhydrase in Chlamydomonas reinhardtii1
- Identification of Intracellular Carbonic Anhydrase in Chlamydomonas reinhardtii with a Carbonic Anhydrase-Directed Photoaffinity Label.
- Effect of CO2 Concentration on Protein Biosynthesis and Carbonic Anhydrase Expression in Chlamydomonas reinhardtii1
- Intracellular carbonic anhydrase of Chlamydomonas reinhardtii.
- CO2-Responsive Transcriptional Regulation of CAH1 Encoding Carbonic Anhydrase Is Mediated by Enhancer and Silencer Regions in Chlamydomonas reinhardtii1