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. ISSN 0021-9258, 1083-351X

Text A paralog of a bacteriochlorophyll biosynthesis enzyme catalyzes the formation of 1,2-dihydrocarotenoids in green sulfur bacteria.pdf - Published version Download (1MB)

Abstract

Chlorobaculum tepidum, 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 C. tepidum contains two paralogous genes encoding members of the FixC family of flavoproteins: bchP, which has been shown to encode an enzyme of bacteriochlorophyll biosynthesis; and bchO, for which a function has not been assigned. Here we demonstrate that a bchO mutant is unable to synthesize 1',2'-dihydrochlorobactene, and when bchO is heterologously expressed in a neurosporene-producing mutant of the purple bacterium, Rhodobacter sphaeroides, 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, Blastochloris viridis. Identification of this enzyme completes the pathways for the synthesis of photosynthetic pigments in Chlorobiaceae, and accordingly and consistent with its role in carotenoid biosynthesis, we propose to rename the gene cruI. Notably, the absence of cruI in B. viridis 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:	22 May 2026 20:38
DOI:	10.1074/jbc.RA118.004672
Related Websites:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3031301
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