BaCopA, a Cu(I) ATPase from the Antarctic bacterium Bizionia argentinensis

NOELIA I. BURGARDT; MELIAN, NOELIA A.; F LUIS GONZÁLEZ FLECHA

Congreso; 20th IUPAB International Congress, 45th SBBf Congress and 50th Annual Meeting of SBBq; 2021

INTERNATIONAL UNION FOR PURE AND APPLIED BIOPHYSICS

INTRODUCTIONCopper ions are cofactor for several enzymes and participate in some cellular redox reactions. Intracellular excess of copper ions generates reactive radicals that cause damage to DNA, proteins and lipids. For this reason, intracellular levels must be regulated to avoid toxic concentrations. A subfamily of P-ATPases (denoted as PIB-1) are present in prokaryotic and eukaryotic organisms, and constitute one of the main transporters responsible for the elimination of excess copper ions from the cytosol.OBJECTIVESIn this work we characterize a putative PIB-type ATPase belonging to ⟨i⟩Bizionia argentinensis⟨/i⟩(BaCopA), a gram-negative bacterium isolated from the superficial seawater of Potter Cove, Antarctica.MATERIALS AND METHODSBaCopA was cloned and expressed in ⟨i⟩Saccharomyces cerevisiae⟨/i⟩ as a GFP-fusion His-tagged protein for its subsequent purification and detection.DISCUSSION AND RESULTSActivity assays indicate that purified BaCopA is able to catalyze ATP hydrolysis at 5°C. ATPase activity of BaCopA increases when Cu (I) and ATP are added to the reaction medium.However, an inhibitory effect of ATPase activity occurs with the addition of vanadate, a specific inhibitor of P-ATPase-type enzymes.A structural model was built by homology modeling using the resolved structure of ⟨i⟩L. pneumophila⟨/i⟩CopA as template (PDB: 4BBJ). The structural alignment shows a high degree of similarity, with the typical topological pattern of PIB-1 ATPases.CONCLUSIONComparison with its mesophilic and hyperthermophilic counterparts led to the identification of key residues conserved in functional domains and differences in non-covalent interactions and surface charges. The detailed analysis of this interaction network suggests greater structural flexibility in BaCopA and, therefore, a better adaptation to low temperatures.