The role of streptavidin and its variants in catalysis by biotinylated secondary amines.

Here, we combine the use of host screening, protein crystallography and QM/MM molecular dynamics simulations to investigate how the protein structure affects iminium catalysis by biotinylated secondary amines in a model 1,4 conjugate addition reaction. Monomeric streptavidin (M-Sav) lacks a quaternary structure and the solvent-exposed reaction site resulted in poor product conversion in the model reaction with low enantio- and regioselectivities. These parameters were much improved when the tetrameric host T-Sav was used; indeed, residues at the symmetrical subunit interface were proven to be critical for catalysis through a mutagenesis study. The use of QM/MM simulations and the asymmetric dimeric variant D-Sav revealed that both Lys121 residues which are located in the hosting and neighboring subunits play a critical role in controlling the stereoselectivity and reactivity. Lastly, the D-Sav template, though providing a lower conversion than that of the symmetric tetrameric counterpart, is likely a better starting point for future protein engineering because each surrounding residue within the asymmetric scaffold can be refined for secondary amine catalysis.

Citation

Alexander R Nödling, Nicolò Santi, Raquel Castillo, Magdalena Lipka-Lloyd, Yi Jin, Louis C Morrill, Katarzyna Świderek, Vicent Moliner, Louis Y P Luk. The role of streptavidin and its variants in catalysis by biotinylated secondary amines. Organic & biomolecular chemistry. 2021 Dec 08;19(47):10424-10431

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PMID: 34825690

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