title: Radical use of Rossmann and TIM barrel architectures for controlling coenzyme B12 chemistry.
abstract: The ability of enzymes to harness free-radical chemistry allows for some of the most amazing transformations in nature, including reduction of ribonucleotides and carbon skeleton rearrangements. Enzyme cofactors involved in this chemistry can be large and complex, such as adenosylcobalamin (coenzyme B(12)), simpler, such as S-adenosylmethionine and an iron-sulfur cluster (i.e., poor man's B(12)), or very small, such as one nonheme iron atom coordinated by protein ligands. Although the chemistry catalyzed by these enzyme-bound cofactors is unparalleled, it does come at a price. The enzyme must be able to control these radical reactions, preventing unwanted chemistry and protecting the enzyme active site from damage. Here, we consider a set of radical folds: the (β/α)(8) or TIM barrel, combined with a Rossmann domain for coenzyme B(12)-dependent chemistry. Using specific enzyme examples, we consider how nature employs the common TIM barrel fold and its Rossmann domain partner for radical-based chemistry.
authors.affiliation: Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Dowling
authors.forename: Anna K
authors.initials: AK
authors.lastname: Croft
authors.forename: Catherine L
authors.initials: CL
authors.lastname: Drennan
mesh_terms: D001419:Bacteria / Q000737:chemistry* / Q000201:enzymology; D002384:Catalysis; D020134:Catalytic Domain; D003038:Cobamides / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D019751:Intramolecular Transferases / Q000737:chemistry / Q000378:metabolism; D007501:Iron / Q000378:metabolism; D008024:Ligands; D008765:Methylmalonyl-CoA Mutase / Q000737:chemistry / Q000378:metabolism; D012436:S-Adenosylmethionine / Q000737:chemistry / Q000378:metabolism; D014805:Vitamin B 12 / Q000737:chemistry / Q000378:metabolism
chemical_list: D003038:Cobamides; D005609:Free Radicals; D008024:Ligands; D012436:S-Adenosylmethionine; D007501:Iron; D019751:Intramolecular Transferases; D008765:Methylmalonyl-CoA Mutase; C000913:cobamamide; D014805:Vitamin B 12