Total synthesis and biochemical characterization of mirror image barnase

Abstract

In this study we synthesized and characterized mirror image barnase (B. amyloliquefaciens ribonuclease). D-Barnase was identical to L-barnase, when analyzed by liquid chromatography and mass-spectrometry. Proteolysis of the mirror image enzyme revealed that in contrast to its native counterpart, D-barnase was completely stable to digestive proteases. In enzymatic assays, D-barnase had the reciprocal chiral specificity and was fully active towards mirror image substrates. Interestingly, D-barnase also hydrolyzed the substrate of the native chirality, albeit 4000 times less efficiently. This effect was further confirmed by digesting a native 112-mer RNA with the enzyme. Additional studies revealed that barnase accommodates a range of substrates with various chiralities, but the prime requirement for guanosine remains. These studies point toward using mirror image enzymes as modern agents in biotechnology.