Nucleotide-based second messengers play important biological functions in living organisms. Among various second messenger molecules, several of them are generated by families of NTases that belong to Polb superfamily. In animals, cytosolic NTases OAS and cGAS generate 2?-5?-linked oligoadenylates and 2?- 5?-linked c-GAMP, respectively, both of which trigger innate immune response against viral and bacterial infection. In bacteria, NTase DncV generates 3?-5?-linked cGAMP, which activates CapV to inhibit cell growth. Using a combination of comparative genomics, sequence conservation, and structure analysis, Aravind and coworkers uncovered a vast network of nucleotide-centric systems in bacteria. A family of NTases named SMODS (secondary messenger oligo and dinucleotides synthase) was predicted to generate second messengers. And several conserved domains were predicted to be receptors of the second messengers generated by SMODS. Among the predicted receptors, the domain named SAVED (SMODS-associated and fused to various effector domains) is the most abundant. With the exception of a recent characterization of the product generated by one of SMODS, however, the predicted biochemical and biological functions of SMODS and SAVED have not been experimentally tested. Employing approaches of bioinformatics, biochemistry, and structural biology, we aim to pursue the following two lines of investigation of SMODS and SAVED: 1) We will in vitro reconstitute the enzymatic activity of SMODS and probe interaction between SAVED and the second messengers generated by SMODS; and 2) We will carry out structural studies of SMODS and SAVED, SMODS in complex with its activator and substrates, and SAVED in complex with the second messengers generated by SMODS.

Public Health Relevance

The proposed studies are likely to discover new second messenger molecules, which could be explored as potentially new therapeutics. In addition, most operons encoding SMODS and SAVED are mobile genetic elements, and their acquisitions by certain strains of bacteria are likely to result in their selective advantage and more pathogenetic. Therefore, blocking the biological processes of SMODS and SAVED could also be explored as a new strategy to inhibit those bacterial pathogens.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Exploratory/Developmental Grants (R21)
Project #
5R21AI150229-02
Application #
10078261
Study Section
Special Emphasis Panel (ZRG1)
Program Officer
Ernst, Nancy L
Project Start
2020-01-01
Project End
2021-12-31
Budget Start
2021-01-01
Budget End
2021-12-31
Support Year
2
Fiscal Year
2021
Total Cost
Indirect Cost
Name
University of Illinois Urbana-Champaign
Department
Biochemistry
Type
Schools of Arts and Sciences
DUNS #
041544081
City
Champaign
State
IL
Country
United States
Zip Code
61820