Functional and fluorescence analyses of tryptophan residues in H +-pyrophosphatase of Clostridium tetani

Yen Wei Chen, Ching Hung Lee, Yun Tzu Huang, Yih Jiuan Pan, Shih Ming Lin, Yueh Yu Lo, Chien Hsien Lee, Lin Kun Huang, Yu Fen Huang, Yu Di Hsu, Rong Long Pan

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Abstract

Homodimeric proton-translocating pyrophosphatase (H+-PPase; EC 3.6.1.1) maintains the cytoplasmic pH homeostasis of many bacteria and higher plants by coupling pyrophosphate (PPi) hydrolysis and proton translocation. H+-PPase accommodates several essential motifs involved in the catalytic mechanism, including the PPi binding motif and Acidic I and II motifs. In this study, 3 intrinsic tryptophan residues, Trp-75, Trp-365, and Trp-602, in H+-PPase from Clostridium tetani were used as internal probes to monitor the local conformational state of the periplasm domain, transmembrane region, and cytoplasmic domain, respectively. Upon binding of the substrate analog Mg-imidodiphosphate (Mg-IDP), local structural changes prevented the modification of tryptophan residues by N-bromosuccinimide (NBS), especially at Trp-602. Following Mg-Pi binding, Trp-75 and Trp-365, but not Trp-602, were slightly protected from structural modifications by NBS. These results reveal the conformation of H +-PPase is distinct in the presence of different ligands. Moreover, analyses of the Stern-Volmer relationship and steady-state fluorescence anisotropy also indicate that the local structure around Trp-602 is more exposed to solvent and varied under different environments. In addition, Trp-602 was identified to be a crucial residue in the H+-PPase that may potentially be involved in stabilizing the structure of the catalytic region by site-directed mutagenesis analysis.

Original languageEnglish
Pages (from-to)127-134
Number of pages8
JournalJournal of Bioenergetics and Biomembranes
Volume46
Issue number2
DOIs
Publication statusPublished - 2014 Apr

All Science Journal Classification (ASJC) codes

  • Physiology
  • Cell Biology

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    Chen, Y. W., Lee, C. H., Huang, Y. T., Pan, Y. J., Lin, S. M., Lo, Y. Y., Lee, C. H., Huang, L. K., Huang, Y. F., Hsu, Y. D., & Pan, R. L. (2014). Functional and fluorescence analyses of tryptophan residues in H +-pyrophosphatase of Clostridium tetani. Journal of Bioenergetics and Biomembranes, 46(2), 127-134. https://doi.org/10.1007/s10863-013-9532-x