Engineered biosynthesis of bacteriochlorophyll g<sub>F</sub> in <i>Rhodobacter</i> <i>sphaeroides</i>

Ortega-Ramos, Marcia, Canniffe, Daniel P ORCID: 0000-0002-5022-0437, Radle, Matthew I, Hunter, C Neil, Bryant, Donald A and Golbeck, John H
(2018) Engineered biosynthesis of bacteriochlorophyll g<sub>F</sub> in <i>Rhodobacter</i> <i>sphaeroides</i>. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS, 1859 (7). pp. 501-509.

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Engineering photosynthetic bacteria to utilize a heterologous reaction center that contains a different (bacterio) chlorophyll could improve solar energy conversion efficiency by allowing cells to absorb a broader range of the solar spectrum. One promising candidate is the homodimeric type I reaction center from Heliobacterium modesticaldum. It is the simplest known reaction center and uses bacteriochlorophyll (BChl) g, which absorbs in the near-infrared region of the spectrum. Like the more common BChls a and b, BChl g is a true bacteriochlorin. It carries characteristic C3-vinyl and C8-ethylidene groups, the latter shared with BChl b. The purple phototrophic bacterium Rhodobacter (Rba.) sphaeroides was chosen as the platform into which the engineered production of BChl g<sub>F</sub>, where F is farnesyl, was attempted. Using a strain of Rba. sphaeroides that produces BChl b<sub>P</sub>, where P is phytyl, rather than the native BChl a<sub>P</sub>, we deleted bchF, a gene that encodes an enzyme responsible for the hydration of the C3-vinyl group of a precursor of BChls. This led to the production of BChl g<sub>P</sub>. Next, the crtE gene was deleted, thereby producing BChl g carrying a THF (tetrahydrofarnesol) moiety. Additionally, the bchG<sup>Rs</sup> gene from Rba. sphaeroides was replaced with bchG<sup>Hm</sup> from Hba. modesticaldum. To prevent reduction of the tail, bchP was deleted, which yielded BChl g<sub>F</sub>. The construction of a strain producing BChl g<sub>F</sub> validates the biosynthetic pathway established for its synthesis and satisfies a precondition for assembling the simplest reaction center in a heterologous organism, namely the biosynthesis of its native pigment, BChl g<sub>F</sub>.

Item Type: Article
Uncontrolled Keywords: Photosynthesis, Heliobacteria, Purple bacteria, Bacteriochlorophyll g, Biosynthetic pathway
Depositing User: Symplectic Admin
Date Deposited: 17 Jan 2019 09:27
Last Modified: 09 Oct 2023 10:56
DOI: 10.1016/j.bbabio.2018.02.006
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