A paralog of a bacteriochlorophyll biosynthesis enzyme catalyzes the formation of 1,2-dihydrocarotenoids in green sulfur bacteria


Canniffe, Daniel P ORCID: 0000-0002-5022-0437, Thweatt, Jennifer L, Chew, Aline Gomez Maqueo, Hunter, C Neil and Bryant, Donald A (2018) A paralog of a bacteriochlorophyll biosynthesis enzyme catalyzes the formation of 1,2-dihydrocarotenoids in green sulfur bacteria. JOURNAL OF BIOLOGICAL CHEMISTRY, 293 (39). pp. 15233-15242.

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Abstract

<i>Chlorobaculum tepidum</i>, a green sulfur bacterium, utilizes chlorobactene as its major carotenoid, and this organism also accumulates a reduced form of this monocyclic pigment, 1',2'-dihydrochlorobactene. The protein catalyzing this reduction is the last unidentified enzyme in the biosynthetic pathways for all of the green sulfur bacterial pigments used for photosynthesis. The genome of <i>C. tepidum</i> contains two paralogous genes encoding members of the FixC family of flavoproteins: <i>bchP</i>, which has been shown to encode an enzyme of bacteriochlorophyll biosynthesis; and <i>bchO</i>, for which a function has not been assigned. Here we demonstrate that a <i>bchO</i> mutant is unable to synthesize 1',2'-dihydrochlorobactene, and when <i>bchO</i> is heterologously expressed in a neurosporene-producing mutant of the purple bacterium, <i>Rhodobacter sphaeroides</i>, the encoded protein is able to catalyze the formation of 1,2-dihydroneurosporene, the major carotenoid of the only other organism reported to synthesize 1,2-dihydrocarotenoids, <i>Blastochloris viridis</i> Identification of this enzyme completes the pathways for the synthesis of photosynthetic pigments in <i>Chlorobiaceae</i>, and accordingly and consistent with its role in carotenoid biosynthesis, we propose to rename the gene <i>cruI</i> Notably, the absence of <i>cruI</i> in <i>B. viridis</i> indicates that a second 1,2-carotenoid reductase, which is structurally unrelated to CruI (BchO), must exist in nature. The evolution of this carotenoid reductase in green sulfur bacteria is discussed herein.

Item Type: Article
Uncontrolled Keywords: photosynthesis, photosynthetic pigment, carotenoid, bacterial genetics, energy metabolism, Blastochloris viridis, Chlorobaculum tepidum, green sulfur bacterium, Rhodobacter sphaeroides
Depositing User: Symplectic Admin
Date Deposited: 17 Jan 2019 09:30
Last Modified: 19 Jan 2023 01:06
DOI: 10.1074/jbc.RA118.004672
Related URLs:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3031301
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