Structural and Functional Characterization of a Short-Chain Flavodoxin Associated with a Noncanonical 1,2-Propanediol Utilization Bacterial Microcompartment

Journal Article · 21 September 2017 · Biochemistry

DOI: https://doi.org/10.1021/acs.biochem.7b00682 · OSTI ID:1422561

Plegaria, Jefferson S. ^[1]; Sutter, Markus ^[2]; Ferlez, Bryan ^[1]; Aussignargues, Clement ^[1]; Niklas, Jens  ^[3]; Poluektov, Oleg G. ^[3]; Fromwiller, Ciara ^[1]; TerAvest, Michaela ^[4]; Utschig, Lisa M.  ^[3]; Tiede, David M. ^[3]; Kerfeld, Cheryl A.  ^[5]

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1. Michigan State Univ., East Lansing, MI (United States). MSU-DOE Plant Research Lab.
2. Michigan State Univ., East Lansing, MI (United States). MSU-DOE Plant Research Lab.; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Molecular Biophysics and Integrated Bioimaging Division
3. Argonne National Lab. (ANL), Argonne, IL (United States). Solar Energy Conversion Group
4. Michigan State Univ., East Lansing, MI (United States). Dept. of Biochemistry & Molecular Biology
5. Michigan State Univ., East Lansing, MI (United States). MSU-DOE Plant Research Lab.; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Molecular Biophysics and Integrated Bioimaging Division; Michigan State Univ., East Lansing, MI (United States). Dept. of Biochemistry & Molecular Biology; Berkeley Synthetic Biology Inst., Berkeley, CA (United States)

Bacterial microcompartments (BMCs) are proteinaceous organelles that encapsulate enzymes involved in CO₂ fixation (carboxysomes). or carbon catabolism (metabolosomes). Metabolosomes share a common core of enzymes and a distinct signature enzyme for substrate degradation that defines the function of the BMC (e,g., propanediol or ethanolamine utilization BMCs, or glycyl-radical enzyme microcompartments). Loci encoding metabolosomes also typically contain genes for proteins that support organelle function, such as regulation, transport of substrate, and cofactor (e.g., vitamin B-12) synthesis and recycling. Flavoproteins are frequently among these ancillary gene products, suggesting that these redox active proteins play an undetermined function in many metabolosomes. Here in this paper, we report the first characterization of a BMC-associated flavodoxin (Fld1C), a small flavoprotein, derived from the noncanonical 1,2-propanediol utilization BMC locus (PDU1C) of Lactobacillus reuteri. The 2.0 angstrom X-ray structure of Fld1C displays the alpha/beta flavodoxin fold, which noncovalently binds a single flavin mononucleotide molecule. Fld1C is a short-chain flavodoxin with redox potentials of -240 +/- 3 mV oxidized/semiquinone and -344 +/- 1 mV semiquinone/hydroquinone versus the standard hydrogen electrode at pH 7.5. It can participate in an electron transfer reaction with a photoreductant to form a stable semiquinone species. Collectively, our structural and functional results suggest that PDU1C BMCs encapsulate Fld1C to store and transfer electrons for the reactivation and/or recycling of the B₁₂ cofactor utilized by the signature enzyme.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: AC02-06CH11357
• OSTI ID: 1422561
• Journal Information: Biochemistry, Vol. 56, Issue 42; ISSN 0006-2960
• Publisher: American Chemical Society (ACS)Copyright Statement
• Country of Publication: United States
• Language: English