Effects of Ice Nucleation Protein Repeat Number and Oligomerization Level on Ice Nucleation Activity

M. L. Ling, H. Wex, S. Grawe, J. Jakobsson, J. Londahl, S. Hartmann, K. Finster, T. Boesen*, T. Santl-Temkiv

*Corresponding author for this work

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review

35 Citations (Scopus)

Abstract

Ice nucleation active bacteria have attracted particular attention due to their unique ability to produce specific ice nucleation proteins (INpros), which are the most efficient ice nuclei known as they induce nucleation at temperatures close to 0°C. Our model bacterium Pseudomonas syringae strain R10.79 produced INpros containing 67 tandem repeats, forming the proposed ice-binding surface. To understand the role of the INpro repeats as well as the role of intermolecular interactions between INpros for their ice nucleation behavior, we produced a truncated version of the protein with only 16 tandem repeats (INpro 16R). The purified INpro 16R produced oligomers of varying sizes. Immersion freezing ice nucleation behavior of purified INpro 16R was characterized by droplet-freezing assays and in the Leipzig Aerosol Cloud Interaction Simulator. Predominant INpro 16R oligomers introduced into Leipzig Aerosol Cloud Interaction Simulator as single particles with diameters of 50 nm or 70 nm were ice nucleation active at temperatures of −26°C and −24°C, respectively. These are much lower temperatures compared to that of intact INpros (−12°C). The data clearly indicated that the number of repeats determines the ice nucleation temperature. In addition, ice nucleation between −9°C and −10°C, comparable to the activity of intact INpro, was caused by higher-order INpro 16R oligomers. This supported previous observations that INpro oligomerization increases the ice-binding surface, thereby affecting ice nucleation activity. In conclusion, both repeat number and oligomerization contribute in a seemingly independent manner to the nucleation mechanism of INpros.

Original languageEnglish
JournalJournal of Geophysical Research: Atmospheres
Volume123
Issue3
Pages (from-to)1802-1810
Number of pages9
ISSN2169-897X
DOIs
Publication statusPublished - 16 Feb 2018

Keywords

  • precipitation
  • bioaerosols
  • PSEUDOMONAS-SYRINGAE
  • BACTERIA
  • PRECIPITATION
  • NUCLEI
  • PLANTS
  • IMPACT
  • MODEL

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