کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1942237 | 1052597 | 2013 | 5 صفحه PDF | دانلود رایگان |
• A biosynthetic pathway to form the C8-ethylidene group for bacteriochlorophyll g was revealed.
• All the gene products for bacteriochlorophyll g biosynthesis were therefore assigned.
• The finding led to two possible branching pathways for biosynthesis of 81-hydroxy-chlorophyll a in heliobacteria.
Heliobacteria have the simplest photosynthetic apparatus, i.e., a type-I reaction center lacking a peripheral light-harvesting complex. Bacteriochlorophyll (BChl) g molecules are bound to the reaction center complex and work both as special-pair and antenna pigments. The C8-ethylidene group formation for BChl g is the last missing link in biosynthetic pathways for bacterial special-pair pigments, which include BChls a and b as well. Here, we report that chlorophyllide a oxidoreductase (COR) of Heliobacterium modesticaldum catalyzes the C8-ethylidene formation from 8-vinyl-chlorophyllide a, producing bacteriochlorophyllide g, the direct precursor for BChl g without the farnesyl tail. The finding led to plausible biosynthetic pathways for 81-hydroxy-chlorophyll a, a primary electron acceptor from the special pair in heliobacterial reaction centers. Proposed catalytic mechanisms on hydrogenation reaction of the ethylidene synthase-type CORs are also discussed.
Journal: Biochimica et Biophysica Acta (BBA) - Bioenergetics - Volume 1827, Issue 10, October 2013, Pages 1200–1204