2.A.62 The NhaD Na+:H+ Antiporter (NhaD) Family The NhaD Na⁺/H⁺ antiporter has been characterized from two Vibrio species: V. parahaemolyticus and V. cholerae (Nozaki et al., 1998; Ostroumov et al., 2002). These proteins and their homologues are about 420 aas long and exhibit 10-12 TMSs. They catalyze Na⁺/H⁺ and Li⁺/H⁺ antiport. They exhibit activity at basic pH (8-9) with no activity at pH 7. Homologues are found in proteobacteria. The NhaD family is a constituent of the IT superfamily (S. Prakish et al., unpublished paper). The generalized reaction catalyzed by NhaD is: nH⁺ (in) + mNa⁺ (out) nH⁺ (out) + mNa⁺ (in). (n and m are unknown, but are probably 1 or 2)
This family belongs to the IT Superfamily.
References:
Nozaki, K., T. Kuroda, T. Mizushima, and T. Tsuchiya. (1998). A new Na⁺/H⁺ antiporter, NhaD, of Vibrio parahaemolyticus. Biochim. Biophys. Acta 1369: 213-220.
Ostroumov, E., J. Dzioba, P. Loewen, and P. Dibrov. (2002). Asp³⁴⁴ and Thr³⁴⁵ are critical for cation exchange mediated by NhaD, Na⁺/H⁺ antiporter of Vibrio cholerae. Biochim. Biophys. Acta 1564: 99-106.
Examples:
TC#	Name	Organismal Type	Example
2.A.62.1.1	NhaD Na⁺/H⁺ antiporter	Bacteria	NhaD of Vibrio parahaemolyticus