We cloned novel Na+-ATPase (HANA) cDNA from marine alga Heterosigma akashiwo. The full-length HANA cDNA was 4467 bp long and coded for a 1330 amino acid protein with a molecular weight of 146 306. The deduced product exhibited around 40% identity in amino acids with Na+/K+-ATPase alpha -subunits. A hydrophilic sequence of 285 amino acid residues that showed no homology with any sequence listed in databases existed in the M7-M8 junction of HANA. This is the first report on the primary structure of putative Na+-transporting ATPase from plant cells. (C) 2001 Elsevier Science B.V. All rights reserved.