Homology Modeling of an Algal Membrane Protein, Heterosigma Akashiwo Na+–ATPase

抄録

The three–dimensional structure of Heterosigma akashiwo Na+–ATPase (HANA) was predicted by means of homology modeling based on the crystal structure of the K+–bound form of shark Na+/K+–ATPase (PDB ID: 2ZXE). The overall structure of HANA appears to be similar to that of shark Na+/K+–ATPase. Both contain three characteristic cytoplasmic domains, A, N and P, which are unique to P–type ATPases. HANA has a long TM7–8 junction as a large extracellular domain, in place of the β–subunit of shark Na+/K+–ATPase. Two putative K+–binding sites in the transmembrane domain of HANA were identified by means of valence mapping based on the constructed structure. The presence of K+–binding sites and the reported ion requirements for ATPase activity and EP formation indicate that HANA may transport K+ ions in the same manner as animal Na+/K+–ATPases.