Fig. 6

Multiple sequence alignment of H⁺-PPase protein sequences. AT1G15690.1, ERN14318, and ERN03082 belong to type I, among which ERN03082 is non-Ia and the rest are Ia. AT1G16780.1 and ERN12531 belong to type II. Transmembrane helices (TM) in the reference sequence (AT1G15690.1) are outlined and numbered, and the six core and ten outer TMs are indicated in black and white, respectively. Arrows indicate key sites in the reference sequence involved in proton transport. Dots indicate the amino acids responsible for functional divergence (Type-I: blue, Type-II: red). The red and blue outlined boxes indicate amino acids that might be responsible for positive selection of type I and type II H⁺-PPases, respectively. Functional disproportionation sites that are responsible for positive selection or involved in proton transport are indicated with green triangles. Black crosses represent key sites for K⁺ demand