2-Methyl-2,4-pentanediol (MPD) boosts as detergent-substitute the performance of ß-barrel hybrid catalyst for phenylacetylene polymerization.

Julia Kinzel,Tino Polen,Andreas Thiel,Tayebeh Mirzaei Garakani,Jun Okuda,Klaus Beckerle,Ulrich Schwaneberg,Marcus Arlt,Daniel F Sauer,Marco Bocola

doi:10.3762/bjoc.13.148

Abstract

Covering hydrophobic regions with stabilization agents to solubilize purified transmembrane proteins is crucial for their application in aqueous media. The small molecule 2-methyl-2,4-pentanediol (MPD) was used to stabilize the transmembrane protein Ferric hydroxamate uptake protein component A (FhuA) utilized as host for the construction of a rhodium-based biohybrid catalyst. Unlike commonly used detergents such as sodium dodecyl sulfate or polyethylene polyethyleneglycol, MPD does not form micelles in solution. Molecular dynamics simulations revealed the effect and position of stabilizing MPD molecules. The advantage of the amphiphilic MPD over micelle-forming detergents is demonstrated in the polymerization of phenylacetylene, showing a ten-fold increase in yield and increased molecular weights.

Highlights

The combination of a transition metal catalyst and a protein by either dative, supramolecular or covalent means leads to so-called artificial metalloenzymes or biohybrid catalysts [1,2].Using a non-natural catalyst, the scope of natural enzymes can be expanded or the activity improved
For solubilizing the transmembrane protein Ferric hydroxamate uptake protein component A (FhuA) ΔCVFtev PE–PEG and MPD were applied as stabilizing agent and phenylacetylene polymerization was performed as model reaction (Figure 1)
Molecular dynamics (MD) simulations of FhuA ΔCVFtev were performed in a box with varying numbers of MPD molecules from 126 MPD, 189 MPD, 252 MPD to 378 MPD molecules as stabilizing cosolvent to investigate the molecular dynamics of protein structure stabilization, how a small amphiphilic molecule could stabilize a transmembrane protein such as FhuA ΔCVFtev

Summary

Introduction

The combination of a transition metal catalyst and a protein by either dative, supramolecular or covalent means leads to so-called artificial metalloenzymes or biohybrid catalysts [1,2].Using a non-natural catalyst, the scope of natural enzymes can be expanded or the activity improved. Nonpolar substrates are poorly soluble in water and often build a second phase or require a cosolvent. To avoid precipitation when using nonpolar substrates, the protein concentration usually is decreased leading to a loss in activity. The polymerization of phenylacetylene was achieved in water by using the robust β-barrel protein nitrobindin. The selectivity in the polymerization of phenylacetylene was influenced with the protein as second ligand sphere [12,13]. The catalyst achieved a cis/trans ratio of 91:9 in the organic solvent tetrahydrofuran (THF) or being bound on a protein surface without a defined protein environment [12]. The productivity remained low due to the decreased protein concentration

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