2.A.70 The Malonate:Na+ Symporter (MSS) Family

The monobasic malonate:Na+ symporter of Malonomonas rubra has been functionally and genetically characterized. It consists of two integral membrane proteins, MadL (129 aas) and MadM (255 aas) which exhibit 4 and 7 putative transmembrane spanners, respectively. The transporter is believed to catalyze the electroneutral reversible uptake of H+-malonate with one Na+, and both subunits have been shown to be essential for activity. There is a close two-subunit homologue in Pseudomonas putida (gbAB017138) which is encoded within the malonate decarboxylase gene cluster of this organism (Chohnan et al., 1999). These proteins apparently comprise a new family of secondary carriers as PSI-BLAST searches do not reveal that they are members of other established families. The NapA Na+/H+ antiporter of Enterococcus hirae (spP26235; CPA2 family, TC #2.A.37) appears to be distantly related to MadM.

The transport reaction catalyzed by MadLM is:

H+ malonate (out) + Na+ (out) ⇌ H+ malonate (in) + Na+ (in).



This family belongs to the CPA Superfamily.

 

References:

Chohnan, S., Y. Kurusu, H. Nishihara, and Y. Takamura. (1999). Cloning and characterization of mdc genes encoding malonate decarboxylase from Pseudomonas putida. FEMS Microbiol. Lett. 174: 311-319.

Schaffitzel, C., M. Berg, P. Dimroth, and K.M. Pos. (1998). Identification of an Na+-dependent malonate transporter of Malonomonas rubra and its dependence on two separate genes. J. Bacteriol. 180: 2689-2693.

Examples:

TC#NameOrganismal TypeExample
2.A.70.1.1The malonate:Na+ symporter, MadLM (MadL, 129aas, 3TMSs; MadM, 255aas, 6TMSs) Bacteria MadLM of Malonomonas rubra
 
2.A.70.1.2The malonate uptake porter, MdcLM (Chohnan et al., 1999)BacteriaMdcLM of Pseudomonas putida:
MdcL (163aas; 4TMSs; Q9Z446)
MdcM (254aas; 8TMSs; Q9Z445)