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-ST10-40^T 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:
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.
Examples:
TC#	Name	Organismal Type	Example
2.A.133.1.1	*Na⁺(Li⁺, K⁺)/H⁺ antiporter of 178 aas and 3 TMSs. It's characterization was described by Shao et al.* 2018 (see family description).**		RDD family protein of Halobacillus andaensis

2.A.133.1.10	Uncharacterized protein of 240 aas and 3 TMSs.	Bacteroidetes	UP of Nonlabens dokdonensis (Donghaeana dokdonensis)

2.A.133.1.11	Uncharacterized protein in the RDD or YckC Family of 151 aas and 3 N-terminal TMSs		YckC of Bacillus subtilis

2.A.133.1.12	RDD family protein of 179 aas and 3-4 TMSs	Bacteria	*RDD family protein of Bacillus pumilus* (B4AEM5)**

2.A.133.1.13	RDD family protein of 159 aas and 3 TMSs.		RDD protein of Helicobacter pylori

2.A.133.1.2	RDD family protein of 133 aas and 3 TMSs	Archaea	*RDD family protein of Methanosarcina barkeri* (Q465I3)**

2.A.133.1.3	Ser/Thr Kinase (N-terminus) linked to a RDD domain (C-terminus) of 3-4 TMSs (492 aas)	Cyanobacteria	*S/T kinase/Rdd domain protein of Nodularia spumigena* (A0ZK04)**

2.A.133.1.4	Human 4TMS RDD protein fused N-terminally to a conserved hydrophilic domain of unknown function (413 aas)	Eukaryotes	*RDD family protein of Homo sapiens* (Q9UBU6)**

2.A.133.1.5	YczC of 127 aas and 3 TMSs; RDD family	Firmicutes	YczC of Bacillus subtilis

2.A.133.1.6	RDD family protein of 408 aas and 3 or 4 N-terminal TMSs		RDD protein of Bdellovibrio bacteriovorus

2.A.133.1.7	RDD family protein of 157 aas and 3 TMSs		RDD protein of Vibrio cholerae

2.A.133.1.8	Uncharacterized RDD protein of 310 aas with 4 C-terminal TMSs.		RDD protein of Stenotrophomonas maltophilia

2.A.133.1.9	RDD family/signal peptidase of 313 aas and 5 TMSs. The first 4 TMSs correspond to the RDD domain-containing family (TC# 2.A.133), while the 5th TMS plus the C-terminal hydrophilic domain corresponds to the signal peptidase domain, belonging to the CAAX peptidease superfamily (TC#s 9.B.1, 9.B.2, 9.B.391 and others (see the CAXX peptidase superfamily).		*Peptidase of Candidatus Levybacteria* bacterium**

Examples:
TC#	Name	Organismal Type	Example
2.A.133.2.1	*RDD motif membrane protein 169 aas and 3 or 4 TMSs, required for growth with acetate as a sole carbon source (Deutschbauer et al.* 2011).**		RDD protein of Shewanella oneidensi

2.A.133.2.2	Uncharacterized RDD motif-containing protein of 182 aas and 4 TMSs.		UP of Collimonas fungivorans

2.A.133.2.3	Uncharacterized RDD family protein of 196 aas and 4 TMSs.		UP of Morococcus cerebrosus

2.A.133.2.4	Uncharacterized RDD domain-containing protein of 157 aas and 3 TMSs		UP of Rhodococcus hoagii

Examples:
TC#	Name	Organismal Type	Example