Identification of the bchP Gene, Encoding Geranylgeranyl Reductase in Chlorobaculum tepidum

Abstract

The Chlorobaculum tepidum genome contains two paralogous genes, CT2256 and CT1232, whose products are members of the FixC dehydrogenase superfamily and have sequence similarity to geranylgeranyl reductases. Each gene was insertionally inactivated, and the resulting mutants were characterized. CT2256 encodes geranylgeranyl reductase (BchP); CT1232 is not involved in bacteriochlorophyll or chlorophyll biosynthesis.

Identification of a Gene Essential for the First Committed Step in the Biosynthesis of Bacteriochlorophyll c

“…This could result in the reduction of ⌬2,6-phytadienol to phytol. Together with previous results showing that BChG lacks substrate specificity for esterifying alcohols (39,40), the presence of elevated levels of Chl a P in the ⌬bciC mutant strongly suggests that the multistep reduction of geranylgeranyl-PPi by BchP happens after, or both before and after, its esterification to (B)Chlide a by BchG or ChlG.…”

“…(B)Pheides methylated at the C-8 2 or C-12 1 positions were detected, but these methylated species were much less abundant than the unmethylated homologs, and the (B)Pheides generally carried only a single methyl group. This is very different from the situation for BChl c synthesis in wildtype cells, in which nearly all BChl c homologs are singly methylated at C-12 1 and most molecules also are singly or doubly methylated at C-8 2 (17). Thus, the C-13 2 -methylcarboxyl group in the substrates apparently lowered the activities of BchQ and BchR.…”

“…phytol) and Chl a (i.e. ⌬2,6-phytadienol) are only catalyzed by one enzyme, BchP, in C. tepidum (39,40). Previous studies had suggested that such selective esterification might be achieved by strict substrate specificity of BchP or the (B)Chl synthases, BchG for BChl a and ChlG for Chl a.…”

“…Other Characteristics of ⌬bciC Deletion Mutant-Previous studies have shown that mutants unable to synthesize BChl c grow much more slowly than wild-type cells at low light intensity (16,17,28). However, wild-type cells exhibit light saturation and grow more slowly at supersaturating light intensities, possibly because of photoinhibition due of exciton quenching in chlorosomes (28).…”

Comparison of Chloroflexus aurantiacus strain J-10-fl proteomes of cells grown chemoheterotrophically and photoheterotrophically

“…A number of proteins critical to the photosynthetic process have been sequenced and characterized, such as proteins involved in the photosynthetic apparatus (Shiozawa et al 1987(Shiozawa et al , 1989Wechsler et al 1987;Vassilieva et al 2002;Feick and Fuller 1984;Frigaard et al 2002;Wechsler et al 1985a), bacteriochlorophyll (BChl) and carotenoid biosynthesis (Lopez et al 1996;Frigaard et al 2006;Chew et al 2008;Chew and Bryant 2007;Bryant et al 2011;Sawicki and Willows 2010), the 3-hydroxypropionate (3-OHP) CO 2 fixation pathway (Zarzycki et al 2008(Zarzycki et al , 2009Xin et al 2009;Hugler et al 2002;Alber and Fuchs 2002;Friedmann et al 2006), and in electron transport chains (Yanyushin et al 2005;Lee et al 2009). The methods employed in these protein discovery and identification efforts, such as sodium dodecyl sulfate-polyacrylamide gel electrophoresis typically require some previous knowledge about the class of proteins of interest.…”