Title: In Vitro Characterization and Concerted Function of Three Core Enzymes of a Glycyl Radical Enzyme - Associated Bacterial Microcompartment

Abstract

Many bacteria encode proteinaceous bacterial microcompartments (BMCs) that encapsulate sequential enzymatic reactions of diverse metabolic pathways. Well-characterized BMCs include carboxysomes for CO₂-fixation, and propanediol- and ethanolamine-utilizing microcompartments that contain B₁₂-dependent enzymes. Genes thus required to form BMCs are typically organized in gene clusters, which promoted their distribution across phyla by horizontal gene transfer. Recently, BMCs associated with glycyl radical enzymes (GREs) were discovered; these are widespread and comprise at least three functionally distinct types. Previously, we predicted one type of these GRE-associated microcompartments (GRMs) represents a B₁₂-independent propanediol-utilizing BMC. We functionally and structurally characterize enzymes of the GRM of Rhodopseudomonas palustris BisB18 and demonstrate their concerted function in vitro. The GRM signature enzyme, the GRE, is a dedicated 1,2-propanediol dehydratase with a new type of intramolecular encapsulation peptide. It forms a complex with its activating enzyme and, in conjunction with an aldehyde dehydrogenase, converts 1,2-propanediol to propionyl-CoA. Notably, homologous GRMs are also encoded in pathogenic Escherichia coli strains. Our high-resolution crystal structures of the aldehyde dehydrogenase lead to a revised reaction mechanism. The successful in vitro reconstitution of a part of the GRM metabolism provides insights into the metabolic function and steps in the assembly of this BMC.

Authors:

Zarzycki, Jan ^[1]; Sutter, Markus ^[2]; Cortina, Niña Socorro ^[1]; Erb, Tobias J. ^[1]; Kerfeld, Cheryl A. ^[3]

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+ Show Author Affiliations

1. Max Planck Inst. for Terrestrial Microbiology, Marburg (Germany)
2. Michigan State Univ., East Lansing, MI (United States). MSU-DOE Plant Research Lab.; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
3. Michigan State Univ., East Lansing, MI (United States). MSU-DOE Plant Research Lab., Dept. of Biochemistry and Molecular Biology; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Berkeley Synthetic Biology Inst., Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States). Dept. of Plant and Microbial Biology

Publication Date:

2017-02-16

Research Org.:

Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1415968

Grant/Contract Number:  

AC02-05CH11231

Resource Type:

Accepted Manuscript

Journal Name:

Scientific Reports

Additional Journal Information:

Journal Volume: 7; Journal ID: ISSN 2045-2322

Publisher:

Nature Publishing Group

Country of Publication:

United States

Language:

English

Subject:

59 BASIC BIOLOGICAL SCIENCES; biochemistry; microbiology; structural biology