identities of 15% and 14%, respectively. This allowed us to extend the structural model from NHE1 to NHE9 (Figure 1B and Figure 2A) and Nhx1 (Figure 1C). To evaluate the Nhx1 and NHE9 models, we examined characteristic traits of membrane proteins, namely the distribution of hydrophobicity and evolutionary conservation. Consistent with the reliability of the models, we show a preponderance of hydrophobic residues within the predicted membrane spans (Figure 1B), and concentration of evolutionarily conserved residues within the core regions of the transporter (Figure 2A).
