Structural basis and synergism of ATP and Na+ activation in bacterial K+ uptake system KtrAB

• Published in: Nature communications Vol. 15; no. 1; p. 3850
• Main Authors: Chiang, Wesley Tien, Chang, Yao-Kai, Hui, Wei-Han, Chang, Shu-Wei, Liao, Chen-Yi, Chang, Yi-Chuan, Chen, Chun-Jung, Wang, Wei-Chen, Lai, Chien-Chen, Wang, Chun-Hsiung, Luo, Siou-Ying, Huang, Ya-Ping, Chou, Shan-Ho, Horng, Tzyy-Leng, Hou, Ming-Hon, Muench, Stephen P., Chen, Ren-Shiang, Tsai, Ming-Daw, Hu, Nien-Jen
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 08.05.2024; Nature Publishing Group; Nature Portfolio
• Subjects: 101/28; 101/58; 631/45/269; 631/535/1258/1259; 631/57/2271; 82/16; 82/80; Adenosine diphosphate; Adenosine Diphosphate - metabolism; Adenosine triphosphate; Adenosine Triphosphate - metabolism; ADP; ATP; Bacillus subtilis; Bacillus subtilis - metabolism; Bacteria; Bacterial Proteins - chemistry; Bacterial Proteins - metabolism; Binding Sites; Cation Transport Proteins - chemistry; Cation Transport Proteins - metabolism; Central nervous system; Channel gating; Channels; Cryoelectron Microscopy; Crystallography; Crystallography, X-Ray; Humanities and Social Sciences; Ligands; Models, Molecular; Molecular biology; multidisciplinary; Nucleotides; Potassium - metabolism; Protein Binding; Science; Science (multidisciplinary); Sodium - metabolism; Synergism; Thermal stability; X-ray crystallography
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-024-48057-y

The K + uptake system KtrAB is essential for bacterial survival in low K + environments. The activity of KtrAB is regulated by nucleotides and Na + . Previous studies proposed a putative gating mechanism of KtrB regulated by KtrA upon binding to ATP or ADP. However, how Na + activates KtrAB and the Na + binding site remain unknown. Here we present the cryo-EM structures of ATP- and ADP-bound KtrAB from Bacillus subtilis (BsKtrAB) both solved at 2.8 Å. A cryo-EM density at the intra-dimer interface of ATP-KtrA was identified as Na + , as supported by X-ray crystallography and ICP-MS. Thermostability assays and functional studies demonstrated that Na + binding stabilizes the ATP-bound BsKtrAB complex and enhances its K + flux activity. Comparing ATP- and ADP-BsKtrAB structures suggests that BsKtrB Arg417 and Phe91 serve as a channel gate. The synergism of ATP and Na + in activating BsKtrAB is likely applicable to Na + -activated K + channels in central nervous system. KtrAB complex is essential in K + uptake for bacteria. Here authors illustrate the synergism of ATP and Na + in activating K+ uptake of KtrAB from Bacillus subtilis and its gating mechanism, which may also shed light on other Na + -activated K + channels.