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Characterization of carbonic anhydrases from Riftia pachyptila , a symbiotic invertebrate from deep‐sea hydrothermal vents
Author(s) -
De Cian MarieCécile,
Bailly Xavier,
Morales Julia,
Strub JeanMarc,
Van Dorsselaer Alain,
Lallier François H.
Publication year - 2003
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.10295
Subject(s) - biochemistry , cytosol , marine invertebrates , biology , carbonic anhydrase , hydrothermal vent , chemistry , enzyme , ecology , hydrothermal circulation , paleontology
The symbiotic hydrothermal vent tubeworm Riftia pachyptila needs to supply its internal bacterial symbionts with carbon dioxide, their inorganic carbon source. Our aim in this study was to characterize the carbonic anhydrase (CA) involved in CO 2 transport and conversion at various steps in the plume and the symbiotic tissue, the trophosome. A complete 1209 kb cDNA has been sequenced from the trophosome and identified as a putative α‐CA based on BLAST analysis and the similarities of total deduced amino‐acid sequence with those from the GenBank database. In the plume, the putative CA sequence obtained from cDNA library screening was 90% identical to the trophosome CA, except in the first 77 nucleotides downstream from the initiation site identified on trophosome CA. A phylogenetic analysis showed that the annelidan Riftia CA (CARp) emerges clustered with invertebrate CAs, the arthropodan Drosophila CA and the cnidarian Anthopleura CA. This invertebrate cluster appeared as a sister group of the cluster comprising mitochondrial and cytosolic isoforms in vertebrates: CAV, CAI II and III, and CAVII. However, amino acid sequence alignment showed that Riftia CA was closer to cytosolic CA than to mitochondrial CA. Combined biochemical approaches revealed two cytosolic CAs with different molecular weights and pI's in the plume and the trophosome, and the occurrence of a membrane‐bound CA isoform in addition to the cytosolic one in the trophosome. The physiologic roles of cytosolic CA in both tissues and supplementary membrane‐bound CA isoform in the trophosome in the optimization of CO 2 transport and conversion are discussed. Proteins 2003;51:327–339. © 2003 Wiley‐Liss, Inc.