The Kamer and Jarvis groups have extensively studied the human steroid carrier protein (SCP-2L) , a single-domain 13.5 kDa protein containing a hydrophobic tunnel, as a scaffold for ArM design. It has been exploited in the design of ArMs for selective hydroformylation using Rhphosphine organometallic complexes , which showed high activity and selectivity in the production of long chain linear aldehydes, under aqueous conditions. Moreover, engineering the scaffold for improved thermostability incurred a five-fold increase in TON compared to the wild type . This protein has also been used in ArMs for the selective oxidation of lignin model compounds , for enantioselective Cu-catalysed Diels-Alder reactions , and artificial photoenzyme design . Other carrier proteins such as adipocyte lipid binding protein (ALBP) , ferric hydroxamate uptake protein component A (FhuA) , and maltose binding protein have been used in the design of ArMs suggesting that proteins with a carrier function may also serve as privileged scaffolds. In this work, the potential of SCP-2L to serve as a privileged protein scaffold is explored, through studying the copper-catalysed 1,4-addition of indole to enones. Bpy is a well-studied ligand for transition metals and is utilised in the coordination sphere of many catalytic complexes 29 . It can be introduced into a protein via the bioconjugation of maleimide or bromomethylbipyridines at cysteine residues (Figure ). Bpy is also one of very few metal ligands that has been incorporated into the genetic code by amber stop codon suppression. Here two methods for site-selective incorporation of bipyridine into the SCP-2L scaffold were compared, and the copper-catalysed 1,4-addition of indole to enones was used to analyse ArM activity. Differences in stereoselectivities were identified with results rationalised using ArM crystal structures and DFT simulations.