Ecology & Evolution seminar series 3 : "Towards an ancient finger print of Rossmann fold enzymes and the evolution of SAM methylation" by Paola Laurino

• Date: April 18 (wed)
• Time: 10:00-11:00
• Venue: C700, Lab3
• Speaker: Prof. Paola Laurino (Protein Engineering and Evolution Unit, OIST)

Towards an ancient finger print of Rossmann fold enzymes and the evolution of SAM methylation

Paola Laurino, PhD

Okinawa Institute of Science and Technology

Email: paola.laurino@oist.jp

Nucleoside-based cofactors are presumed to have preceded proteins. The Rossmann fold is one of the most ancient and functionally diverse protein folds. We analyzed an omnipresent Rossmann ribose binding interaction – a carboxylate side-chain at the tip of the second beta-strand (β2-Asp/Glu). We identified a canonical motif, defined by the β2-topology and unique geometry. This motif is uniquely found in Rossmann enzymes that use different cofactors, primarily SAM, NAD and FAD. Ribose-carboxylate bidentate interactions in other folds are not only rare but also have a different topology and geometry. Overall, these data indicate the divergence of several major Rossmann-fold enzyme classes from a common pre-Last Universal Common Ancestor (LUCA) that possessed the β2-Asp/Glu motif.

While we were studying how Rossmann fold enzyme binding ribose based cofactor evolves, the adenosine mode of binding of SAM to the Rossmann fold methyltransferase enzymes attracted our attention. Based on this observation we decided to further study the evolution of SAM methyltransferases. The origins of SAM methylation are complex, seemingly demanding the simultaneous emergence of an enzyme that makes SAM and enzyme(s) that utilize it. We report that both ATP and adenosine spontaneously react with methionine to yield SAM, thus suggesting that SAM could have emerged by chance. SAM methylation thus exemplifies how metabolites and pathways can co‐emerge through the gradual recruitment of individual enzymes in reverse order.