Protein Residues and a Novel Motif Involved in the Cellular Localization of CheZ in Azorhizobium caulinodans ORS571

Xiaolin Liu; Yanan Liu; Kevin Scot Johnson; Xiaoyan Dong; Zhihong Xie

doi:10.3389/fmicb.2020.585140

Protein Residues and a Novel Motif Involved in the Cellular Localization of CheZ in Azorhizobium caulinodans ORS571

Front Microbiol. 2020 Dec 7:11:585140. doi: 10.3389/fmicb.2020.585140. eCollection 2020.

Authors

Xiaolin Liu^{1

2}, Yanan Liu^{1

2}, Kevin Scot Johnson³, Xiaoyan Dong^{1

4}, Zhihong Xie^{1

4

5}

Affiliations

¹ Key Laboratory of Coastal Environmental Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, China.
² College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China.
³ Department of Microbiology and Environmental Toxicology, University of California, Santa Cruz, Santa Cruz, CA, United States.
⁴ Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China.
⁵ National Engineering Laboratory for Efficient Utilization of Soil and Fertilizer Resources, College of Resources and Environment of Shandong Agricultural University, Taian, China.

Abstract

Chemotaxis is essential for the competitiveness of motile bacteria in complex and harsh environments. The localization of chemotactic proteins in the cell is critical for coordinating a maximal response to chemotactic signals. One chemotaxis protein with a well-defined subcellular localization is the phosphatase CheZ. CheZ localizes to cell poles by binding with CheA in Escherichia coli and other enteric bacteria, or binding with a poorly understood protein called ChePep in epsilon-Proteobacteria. In alpha-Proteobacteria, CheZ lacks CheA-binding sites, and its cellular localization remains unknown. We therefore determined the localization of CheZ in the alpha-Proteobacteria Azorhizobium caulinodans ORS571. A. caulinodans CheZ, also termed as CheZ_AC, was found to be located to cell poles independently of CheA, and we suspect that either the N-terminal helix or the four-helix bundle of CheZ_AC is sufficient to locate to cell poles. We also found a novel motif, AXXFQ, which is adjacent to the phosphatase active motif DXXXQ, which effects the monopolar localization of CheZ_AC. This novel motif consisting of AXXFQ is conserved in CheZ and widely distributed among Proteobacteria. Finally, we found that the substitution of phosphatase active site affects the polar localization of CheZ_AC. In total, this work characterized the localization pattern of CheZ containing a novel motif, and we mapped the regions of CheZ_AC that are critical for its polar localization.

Keywords: Azorhizobium caulinodans; CheZ; cellular localization; chemotaxis; rhizobia.