Poster: Lipids & Related Molecules

Abs # 858: Enzymes of betaine lipid biosynthesis in photosynthetic bacteria and algae.

Presenter:	Riekhof, Wayne , riekhofw@msu.edu
Authors	Riekhof, Wayne  (A) (B)  Ruckle, Michael  (A)   Lydic, Todd  (A)   Benning, Christoph  (A)
Affiliations:	(A): Michigan State University, Dept. of Biochemistry and Molecular Biology (B): MSU-DOE Plant Research Laboratory

Many algae and photosynthetic gram-negative bacteria have the ability to alter the composition of their cellular membranes in response to phosphate deprivation. In Rhodobacter sphaeroides, one component of this response involves synthesis of the betaine-lipid diacylglycerol-N,N,N-trimethylhomoserine (DGTS), possibly to replace phosphatidylcholine. Two enzymes of R. sphaeroides involved in DGTS biosynthesis, BtaA and BtaB, were previously identified in our laboratory. This work describes the production of recombinant BtaA and BtaB in E. coli, and the subsequent biochemical and kinetic characterization of the recombinant enzymes. BtaA was found to catalyze the transfer of the 3-amino-3-carboxypropyl portion of S-adenosyl methionine (AdoMet) to the 3-hydroxyl of diacylglycerol in vitro. The enzyme was shown to be associated with the cellular membranes, possibly via an N-terminal domain capable of forming an amphipathic helix. The similarity of BtaA to other classes of AdoMet utilizing enzymes is also discussed. In addition, a genetic/genomic approach to the identification of DGTS biosynthetic enzymes in Chlamydomonas reinhardtii has resulted in the isolation of novel mutants in the DGTS pathway, and the DGTS biosynthetic enzymes in C. reinhardtii are described.