Part of the UhpABC signaling cascade that controls the expression of the hexose phosphate transporter UhpT. UhpC senses external glucose-6-phosphate and interacts with the histidine kinase UhpB, leading to the stimulation of the autokinase activity of UhpB. Belongs to the major facilitator superfamily. Organophosphate:Pi antiporter (OPA) (TC 2.A.1.4) family.