The Role of Arginine 28 in Catalysis by Dihydrofolate Reductase from the Hyperthermophile Thermotoga maritima

(Figure Presented) Get a grip: Dihydrofolate reductase from Thermotoga maritima (TmDHFR) is unusual in that it has an arginine residue within its active site (ringed residue). Here, we address the role of this residue in catalysis. We find no evidence that Arg28 compromises catalysis in TmDHFR by preventing protonation of the substrate or that it acts as an acid to protonate the substrate. Instead, it appears that this residue plays an important role in binding the substrate tightly to ensure its thermal stability. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA.