A RubisCO like protein links SAM metabolism with isoprenoid biosynthesis

Functional assignment of uncharacterized proteins is a challenge in the era of large-scale genome sequencing. Here, we combine in extracto-NMR, proteomics, and transcriptomics with a newly developed (knock-out) metabolomics platform to determine a potential physiological role for a ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO)-like protein (RLP) from Rhodospirillum rubrum. Our studies unravelled an unexpected link in bacterial central carbon metabolism between S-adenosylmethionine (SAM)-dependent polyamine metabolism and isoprenoid biosynthesis and also provide an alternative approach to assign enzyme function at the organismic level.