| NSF Org: |
MCB Division of Molecular and Cellular Biosciences |
| Recipient: |
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| Initial Amendment Date: | July 24, 2018 |
| Latest Amendment Date: | May 3, 2021 |
| Award Number: | 1817621 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Marcia Newcomer
mnewcome@nsf.gov (703)292-2357 MCB Division of Molecular and Cellular Biosciences BIO Directorate for Biological Sciences |
| Start Date: | August 1, 2018 |
| End Date: | December 31, 2020 (Estimated) |
| Total Intended Award Amount: | $750,000.00 |
| Total Awarded Amount to Date: | $257,771.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
845 N PARK AVE RM 538 TUCSON AZ US 85721 (520)626-6000 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
1041 E. Lowell Street Tucson AZ US 85721-0008 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | Molecular Biophysics |
| Primary Program Source: |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.074 |
ABSTRACT
Research on biofilms, bacterial communities that coat our teeth when we sleep, has been ongoing for decades. However, even today, the only certain way to remove biofilms is by mechanical force, i.e. a toothbrush. While brushing teeth is routine, removal of biofilms from ships, pipes, medical devices etc., is exceedingly difficult. Formation of biofilms is one of the major survival mechanisms utilized by bacteria, but knowledge of how it occurs is rudimentary. Bacterial persisters, a genetically identical sub-population of quiescent cells that express protein toxins and exhibit multidrug tolerance, are at the core of biofilm formation and in enabling bacteria adapt to changing environmental conditions. Gene pairs known as toxin-antitoxin (TA) systems have emerged as key components of this adaptation process. This project will determine how toxins block bacterial growth by discovering how they inactivate substrates, how they are inhibited by antitoxins and how bacteria remove toxins in order to exit persistence. In addition to helping discover novel approaches for controlling biofilms, the project will provide research training opportunities for students and STEM education opportunities for high school students through implementation of the Protein Science Workshop in the UA BIOTECH outreach project.
Many TA toxins, including MqsR, the focus of this proposal, are ribonucleases (RNases). In order to control biofilm formation, an understanding of how RNase toxins regulate bacterial growth and arrest must be obtained. The research will determine how MqsR recognizes and cleaves mRNA substrates. Preliminary data suggest that this information will lead to a novel mechanism used by RNases to digest mRNA. The project will also identify how antitoxin MqsA inhibits MqsR activity, facilitating development of new approaches for toxin inhibition/modulation. Finally, the molecular determinants that direct MqsA and MqsR proteolysis and turnover in bacteria will be determined. These will define protein recognition sites that can be used to control TA turnover in cells, and provide new insights into the mechanisms used by bacterial proteases to recognize their endogenous substrates. An integrated structural, biochemical and cellular approach will be utilized to address these fundamental questions.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Toxin-antitoxin (TA) systems are regulatory switches that allow bacteria to adapt to rapidly changing environments. Under conditions of growth, these systems are repressed. However, under conditions of stress, these systems are activated, leading to growth arrest and dormancy. Many TA toxins, including MqsR, which is the focus of this proposal, are ribonucleases (RNases). In order to control bacterial growth and especially biofilm formation, we need to understand how RNase toxins arrest bacterial growth, how their cognate antitoxins, i.e., MqsA, block this function and how these proteins are regulated in cells. The work from this grant led to fundamental new discoveries to begin to answer some of these key questions. First, it was discovered that the MqsA antitoxin is specifically degraded by ClpXP and that this degradation requires that MqsA be in a nascent or unfolded state. Second, a novel ClpX N-domain recognition sequence was discovered and shown that when this sequence is added to other proteins, they too are targeted for degradation. The study revealed how MqsR binds mRNA substrates at a molecular level and, further, that MqsA inhibits MqsR activity not by altering its active site but instead by sterically blocking substrate binding. Together, these studies are providing novel strategies to regulate bacterial growth, especially the formation of biofilms, by identifying targetable sites that can directly control the activities of these systems. Finally, in addition to the advances to society that these strategies will provide, this scientific program also advanced the education of multiple graduate and undergraduate students, both directly through their own research, and in the communication of their research to the broader community both at their own institutions and at local and national scientific meetings.
Last Modified: 06/26/2021
Modified by: Rebecca Page
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