Christine Wenjie Zhou

All Publications

• The polar amino acid in the TatA transmembrane helix is not strictly necessary for protein function. The Journal of biological chemistry Hao, B., Zhou, W., Theg, S. M. 2023: 102998

  Abstract

  The twin-arginine translocation (Tat) pathway utilizes the proton-motive force (pmf) to transport folded proteins across cytoplasmic membranes in bacteria and archaea, as well as across the thylakoid membrane in plants and the inner membrane in mitochondria. In most species, the minimal components required for Tat activity consist of three subunits, TatA, TatB, and TatC. Previous studies have shown that a polar amino acid is present at the N-terminus of the TatA transmembrane helix (TMH) across many different species. In order to systematically assess the functional importance of this polar amino acid in the TatA TMH in Escherichia coli, we examined a complete set of 19-amino-acid substitutions. Unexpectedly, although being preferred overall, our experiments suggest that the polar amino acid is not necessary for a functional TatA. Hydrophilicity and helix-stabilizing properties of this polar amino acid were found to be highly correlated with the Tat activity. Specifically, change in charge status of the amino acid side chain due to pH resulted in a shift in hydrophilicity, which was demonstrated to impact the Tat transport activity. Furthermore, we identified a four-residue motif at the N-terminus of the TatA TMH by sequence alignment. Using a biochemical approach, we found that the N-terminal motif was functionally significant, with evidence indicating a potential role in the preference for utilizing different pmf components. Taken together, these findings yield new insights into the functionality of TatA and its potential role in the Tat transport mechanism.

  View details for DOI 10.1016/j.jbc.2023.102998

  View details for PubMedID 36764519

• Hydrophobic mismatch is a key factor in protein transport across lipid bilayer membranes via the Tat pathway JOURNAL OF BIOLOGICAL CHEMISTRY Hao, B., Zhou, W., Theg, S. M. 2021; 298 (7): 101991

  Abstract

  The twin-arginine translocation (Tat) pathway transports folded proteins across membranes in bacteria, thylakoids, plant mitochondria, and archaea. In most species, the active Tat machinery consists of three independent subunits: TatA, TatB, and TatC. TatA and TatB possess short transmembrane alpha helices (TMHs), both of which are only 15 residues long in Escherichia coli. Such short TMHs cause a hydrophobic mismatch between Tat subunits and the membrane bilayer, although the functional significance of this mismatch is unclear. Here, we sought to address the functional importance of the hydrophobic mismatch in the Tat transport mechanism in E. coli. We conducted three different assays to evaluate the effect of TMH length mutants on Tat activity and observed that the TMHs of TatA and TatB appear to be evolutionarily tuned to 15 amino acids, with activity dropping off following any modification of this length. Surprisingly, TatA and TatB with as few as 11 residues in their TMHs can still insert into the membrane bilayer, albeit with a decline in membrane integrity. These findings support a model of Tat transport utilizing localized toroidal pores that form when the membrane bilayer is thinned to a critical threshold. In this context, we conclude that the 15-residue length of the TatA and TatB TMHs can be seen as a compromise between the need for some hydrophobic mismatch to allow the membrane to reversibly reach the threshold thinness required for toroidal pore formation and the permanently destabilizing effect of placing even shorter helices into these energy-transducing membranes.

  View details for DOI 10.1016/j.jbc.2022.101991

  View details for Web of Science ID 000829544300002

  View details for PubMedID 35490783

  View details for PubMedCentralID PMC9207671

• Honeycomb-Spherical Co3O4-TiO2 Hybrid Materials for Enhanced Lithium Storage ELECTROCHIMICA ACTA Li, Y., Shang, K., Zhou, W., Tan, L., Pan, X., Liao, M., Lei, J., Zhao, L. 2016; 222: 1642-1649

  View details for DOI 10.1016/j.electacta.2016.11.153

  View details for Web of Science ID 000395443700078