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Conformational flexibility in the zinc solute-binding protein ZnuA
Elsie Laban Yekwa1, Fred Allen Serrano1, Erik Yukl1
1Department of Chemistry and Biochemistry, New Mexico State University, 1175 North Horseshoe Drive, Las Cruces, NM 88003, USA.
Summary
Citrobacter koseri ZnuA, a zinc transporter, shows unique structural changes compared to similar bacterial proteins. This finding offers new insights into zinc transport mechanisms and potential antibiotic targets.
Area of Science:
- Microbiology
- Structural Biology
- Biochemistry
Background:
- Zinc is essential for all life forms, necessitating efficient cellular transport mechanisms.
- Bacterial ATP-binding cassette (ABC) transporters, utilizing solute-binding proteins (SBPs), mediate high-affinity zinc import.
- These zinc transport systems are crucial for bacterial survival, virulence, and represent potential targets for novel antibiotics.
Purpose of the Study:
- To characterize the high-affinity zinc binding of Citrobacter koseri cluster A-I SBP ZnuA.
- To determine the X-ray crystal structure of the zinc-bound (holo) form of C. koseri ZnuA.
- To compare the structural and functional properties of C. koseri ZnuA with its homologues.
Main Methods:
- X-ray crystallography was employed to determine the structure of zinc-bound C. koseri ZnuA.
- Biochemical characterization of high-affinity zinc binding was performed.
- Comparative structural analysis with ZnuA homologues from Salmonella enterica and Escherichia coli was conducted.
Main Results:
- The crystal structure of zinc-bound C. koseri ZnuA was determined.
- C. koseri ZnuA exhibits a distinct zinc-coordination environment and a closed conformation, differing from its homologue in Salmonella enterica.
- Despite high sequence identity (95%) with Salmonella enterica ZnuA, C. koseri ZnuA displays significant structural differences.
Conclusions:
- Citrobacter koseri ZnuA possesses a unique structural conformation and zinc-binding environment compared to closely related bacterial ZnuA proteins.
- The observed conformational flexibility in ZnuA homologues suggests an adaptable mechanism for efficient zinc acquisition and transport.
- Understanding these structural variations in bacterial zinc transporters can inform the development of targeted antibacterial strategies against pathogens like C. koseri.
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