Part of a K(+) efflux system which is required for the adaptation of R.meliloti to alkaline pH as well as for the infection process during symbiotic nodule development. May form a hetero-oligomeric complex that consists of six subunits: PhaAB, PhaC, PhaD, PhaE, PhaF and PhaG. Belongs to the CPA3 antiporters (TC 2.A.63) subunit G family.