Cyanobacterial KdpD modulates in vivo and in vitro activities of a membrane-anchored histidine kinase

• Published in: Biochimica et biophysica acta. General subjects Vol. 1869; no. 8; p. 130817
• Main Authors: Ballal, Anand, Apte, Shree Kumar
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.07.2025
• Subjects: Anabaena - enzymology; Anabaena - genetics; Anabaena - metabolism; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; cyanobacteria; Escherichia coli - enzymology; Escherichia coli - genetics; Escherichia coli - metabolism; Escherichia coli Proteins - genetics; Escherichia coli Proteins - metabolism; Fusion protein; Gene Expression Regulation, Bacterial; Histidine Kinase - genetics; Histidine Kinase - metabolism; KdpD sensor kinase; Potassium - metabolism; Potassium limitation; Protein Kinases - metabolism; Salt stress; Signal transduction; Signal transduction; Salt stress; KdpD sensor kinase; Fusion protein; Potassium limitation; cyanobacteria
• ISSN: 0304-4165; 1872-8006; 1872-8006
• DOI: 10.1016/j.bbagen.2025.130817

The prokaryotic KdpATPAse complex, encoded by the kdpABC operon, is an inducible, high-affinity K+ transporter. In E. coli, the operon is transcriptionally regulated by a two-component sensor-kinase response-regulator system, constituted by the KdpD and KdpE proteins. In contrast, cyanobacteria exhibit a truncated kdpD gene that encodes a KdpD homolog that is similar to the N-terminal domain (NTD) of E. coli KdpD, but lacks the transmitter, histidine kinase-containing, C-terminal domain (CTD). Here we show that the cyanobacterium Anabaena sp. strain L-31 constitutively transcribes the short kdpD gene, but synthesizes KdpATPase only during potassium starvation. However, unlike E. coli., expression of the kdpD gene remains unaffected by K+ limitation in Anabaena. To gain insight into the possible role of Anabaena KdpD, the chimeric Anacoli KdpD protein, wherein the NTD of E. coli KdpD was replaced with Anabaena KdpD, was functionally analyzed. Detailed investigation has revealed that the Anacoli KdpD (a) responds to a much lower threshold of external K+ than the E. coli KdpD (b) exhibits much reduced ability to induce kdp in response to ionic osmolytes than E. coli KdpD, and is therefore unable to sustain optimal growth in the presence of these osmolytes and (c) displays higher in vitro phosphatase activity than the wild type E. coli KdpD. Thus, Anabaena KdpD modulates properties of E. coli KdpD-CTD in a manner that is quite distinct from the E. coli KdpD-NTD. Based on these evidences, a model for kdp regulation by the short KdpD is proposed. •KdpB polypeptide was synthesized in response to K+ limitation in Anabaena.•Magnitude of kdp induced by Anacoli KdpD was lower than that mediated by E. coli KdpD.•Compared to E. coli KdpD, AncoliKdpD showed a higher phosphatase activity.•N-terminal domain of KdpD modulated activities of the KdpD C-terminal domain.•A model of kdp regulation is proposed for Anabaena.