Coordination and Reductive Cleavage of S-adenosylmethionine by [4Fe-4S]-Maquettes

Katherine Kaul, Garrett Olrogg, Amanda Galambas, Valérie Copié, Joan B. Broderick, Robert K. Szilagyi, and Eric M. Shepard Department of Chemistry and Biochemistry Montana State University, Bozeman, MT 59717

Radical S-adenosylmethionine (SAM) enzymes are a protein superfamily that are a critical component of many living organisms. They function through the coordination of SAM to a [4Fe-4S] cluster and participate in a variety of radical reactions. Radical SAM enzymes all share a highly conserved CX3CX2C consensus motif that is responsible for the coordination of a redox active [4Fe-4S] cluster. The unique iron site associated with this [4Fe-4S] cluster is where SAM coordinates in bidentate fashion through its amino and carboxylate groups. Once the enzyme, cluster, and SAM form a ternary complex, SAM is cleaved to produce the dAdo∙, which is involved in H-atom abstraction from a multitude of substrates including proteins, DNA, and tRNA. Our research utilizes maquettes, which are short peptide sequences that contain the cysteine residues that bind the cluster. Evidence of [4Fe-4S] cluster coordination to the maquette is now well characterized by our lab, but the specific maquette sequence features needed to promote SAM binding to the cluster are still unknown, and SAM cleavage has not been observed. This research project will utilize defined sequences in chemical reconstitution experiments that invoke ferric chloride, sodium sulfide, HEPES buffer, SAM, and beta-mercaptoethanol.  Following [4Fe-4S] cluster synthesis, spectroscopic analysis via UV-vis, Mössbauer, EPR, or LC-MS is completed to determine the presence of cluster formation, peptide coordination, SAM binding, and ideally SAM cleavage. Overall, through this research the goal is to determine the minimal peptide motif necessary for SAM coordination and to investigate what peptide elements are needed to trigger the reductive cleavage of SAM. This is important, because it will promote our understanding of the protein elements that help control radical chemistry in biology. 

Additional Abstract Information

Presenter: Katherine Kaul

Institution: Montana State University

Type: Poster

Subject: Biochemistry

Status: Approved

Time and Location

Session: Poster 1
Date/Time: Mon 1:30pm-2:30pm
Session Number: 2143