Docking analysis of models for 4-hydroxy-3-methylbut-2-enyl diphosphate reductase and a ferredoxin from Botryococcus braunii, race B.

The green microalga Botryococcus braunii Showa, which produces large amounts of triterpene hydrocarbons, exclusively uses the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway for isoprenoid biosyntheses, and the terminal enzyme in this pathway, 4-hydroxy-3-methylbut-2-enyl diphosphate reductase (HDR), is regarded as a light-dependent key regulatory enzyme. In order to investigate the possible association of HDR and ferredoxin in this organism, we constructed tertiary structure models of B. braunii HDR (BbHDR) and one of ferredoxin families in the alga, a photosynthetic electron transport F (BbPETF)-like protein, by using counterparts from E. coli and Chlamydomonas reinhardtii as templates, respectively, and performed docking analysis of these two proteins. After docked models are superimposed onto their counterpart proteins in a non-photosynthetic organism, Plasmodium falciparum, the BbPETF-like protein comes in contact with the backside of BbHDR, which was defined in a previous report (Rekittke et al. 2013), and the distance of the two Fe-S centers is 14.7 Å. This distance is in almost the same level as that for P. falicarum, 12.6 Å. To our knowledge, this is the first model suggesting the possible association of HDR with a ferredoxin in O2-evolving photosynthetic organisms.