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

Effects of Ice Nucleation Protein Repeat Number and Oligomerization Level on Ice Nucleation Activity 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 (INpro16R). The purified INpro16R produced oligomers of varying sizes. Immersion freezing ice nucleation behavior of purified INpro16R was characterized by droplet‐freezing assays and in the Leipzig Aerosol Cloud Interaction Simulator. Predominant INpro16R 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 INpro16R 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. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Geophysical Research: Atmospheres Wiley

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

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Publisher
Wiley Subscription Services, Inc., A Wiley Company
Copyright
©2018. American Geophysical Union. All Rights Reserved.
ISSN
2169-897X
eISSN
2169-8996
D.O.I.
10.1002/2017JD027307
Publisher site
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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 (INpro16R). The purified INpro16R produced oligomers of varying sizes. Immersion freezing ice nucleation behavior of purified INpro16R was characterized by droplet‐freezing assays and in the Leipzig Aerosol Cloud Interaction Simulator. Predominant INpro16R 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 INpro16R 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.

Journal

Journal of Geophysical Research: AtmospheresWiley

Published: Jan 16, 2018

Keywords: ;

References

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