Radical Shuttling in a Protein: Ribose Pseudorotation Controls Alkyl-Radical Transfer in the Coenzyme B(12) Dependent Enzyme Glutamate Mutase This work was supported by the Österreichische Akademie der Wissenschaften (APART fellowship 614), the Österreichische Fonds zur Förderung der wissenschaftlichen Forschung (FWF-project 11599), and the European Commission (TMR project number ERB 4061 PL 95-0307). Crystallographic data were collected at the EMBL-beamline BW7B at DESY in Hamburg, Germany. We thank the beamline scientists for their assistance, and Ingrid Dreveny, Günter Gartler, Gerwald Jogl, and Oliver Sauer for their help during data collection. This research emerged from a collaboration with Prof. W. Buckel (Marburg) who supplied us with clones of the glutamate mutase proteins.