Part of the UhpABC signaling cascade that controls the expression of the hexose phosphate transporter UhpT. UhpB functions as a membrane-associated protein kinase that autophosphorylates in response to interaction with UhpC, and subsequently transfers its phosphate group to the response regulator UhpA (PubMed:3038843, PubMed:8349544, PubMed:11053370, PubMed:11739766). Can also dephosphorylate UhpA (PubMed:11053370, PubMed:11739766). ATP + protein L-histidine = ADP + protein N-phospho-L-histidine. Kinase activity is stimulated by UhpC. Autophosphorylated. Extended N-terminus.