Cloning, sequencing and functional expression in Escherichia coli of the gene for a P-type Na+-ATPase of a facultatively anaerobic alkaliphile, Exiguobacterium aurantiacum

Cloning and sequencing of the gene encoding a P-type Na+-ATPase of a facultatively anaerobic alkaliphile, Exiguobacterium aurantiacum, were conducted. The structural gene was composed of 2628 nucleotides. The deduced amino acid sequence (876 amino acid residues; Mr, 96,664) suggested that the enzyme possesses 10 membrane-spanning regions. When the amino acid sequences of the four putative membrane regions, M4, M5, M6 and M8, of BL77/1 ATPase were aligned with those of fungal Na+-ATPase, Na+/K+-ATPase, H+-ATPases and sarcoplasmic reticulum Ca2+-ATPase, it exhibited the highest homology with Ca2+-ATPase except M5 region. By the transformation of Escherichia coli with the expression vector (pQE30) containing the ATPase gene, the enzyme was functionally expressed in E. coli membranes.