Author's Final Manuscript
The archaeal enzyme geranylgeranyl reductase (GGR) catalyzes hydrogenation of carbon-carbon double bonds to produce the saturated alkyl chains of the organism's unusual isoprenoid-derived cell membrane. Enzymatic reduction of isoprenoid double bonds is of considerable interest both to natural products researchers and to synthetic biologists interested in the microbial production of isoprenoid drug or biofuel molecules. Here we present crystal structures of GGR from Sulfolobus acidocaldarius, including the structure of GGR bound to geranylgeranyl pyrophosphate (GGPP). The structures are presented alongside activity data that depict the sequential reduction of GGPP to H(6)GGPP via the intermediates H(2)GGPP and H(4)GGPP. We then modified the enzyme to generate sequence variants that display increased rates of H(6)GGPP production or are able to halt the extent of reduction at H(2)GGPP and H(4)GGPP. Crystal structures of these variants not only reveal the structural bases for their altered activities; they also shed light onto the catalytic mechanism employed.
This article was originally published in Structure and is also available online here: http://www.sciencedirect.com/science/article/pii/S0969212614001488.
Kung, Y., McAndrew, R. P., Xinkai, X., Liu, Charlie C., Pereira, J. H., Adams, P. D., & Keasling, J. D. "Constructing Tailored Isoprenoid Products by Structure-Guided Modification of Geranylgeranyl Reductase." Structure 22.7 (2014): 1028-1036. DOI: 10.1016/j.str.2014.05.007