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2.A.133.  The RDD Na+(Li+)(K+)/H+ Antiporter (RDD) Family

The arginine-aspartate-aspartate (RDD) family, representing a category of transmembrane proteins containing one highly conserved arginine and two aspartates (RDD) are wide spread in Nature. Shao et al. 2018 characterized a member of this family from the moderate halophile Halobacillus andaensis NEAU-ST10-40T and reported that it functions as a novel Na+(Li+, K+)/H+ antiporter. The highly conserved arginine and aspartate residues are important for the protein's cation-transporting activity.  In fact, D154, R124, R129, and D158 are indispensable for Na+(Li+, K+)/H+ antiport activity whereas neither R35 nor D42 is required for activity (Shao et al. 2018).

References associated with 2.A.133 family:

Shao, L., H. Abdel-Motaal, J. Chen, H. Chen, T. Xu, L. Meng, Z. Zhang, F. Meng, and J. Jiang. (2018). Characterization of a Functionally Unknown Arginine-Aspartate-Aspartate Family Protein From and Functional Analysis of Its Conserved Arginine/Aspartate Residues. Front Microbiol 9: 807. 29922240