Photocatalytic Hydrogen Evolution by a De Novo Designed Metalloprotein that Undergoes Ni‐Mediated Oligomerization Shift

Abstract

De novo metalloprotein design involves the construction of proteins guided by specific repeat patterns of polar and apolar residues, which, upon self-assembly, provide a suitable environment to bind metals and produce artificial metalloenzymes. While a wide range of functionalities have been realized in de novo designed metalloproteins, the functional repertoire of such constructs towards alternative energy-relevant catalysis is currently limited. Here we show the application of de novo approach to design a functional H 2 evolving protein. The design involved the assembly of an amphiphilic peptide featuring cysteines at tandem a/d sites of each helix. Intriguingly, upon Ni II addition, the oligomers shift from a major trimeric assembly to a mix of dimers and trimers. The metalloprotein produced H 2 photocatalytically with a bell-shape pH dependence, having a maximum activity at pH 5.5. Transient absorption spectroscopy is used to determine the timescales of electron transfer as a function of pH. Selective outer sphere mutations are made to probe how the local environment tunes activity. A preferential enhancement of activity is observed via steric modulation above the Ni II site, towards the N-termini, compared to below the Ni II site towards the C-termini.

A De Novo Designed Trimeric Metalloprotein as a Nip Model of the Acetyl-CoA Synthase

“…The solid-state peptide synthesis was performed using a CEM Liberty Blue (Matthews, NC, USA) automated microwave peptide synthesizer as per our earlier reports [ 24 , 32 ].…”

Enzymatic and Bioinspired Systems for Hydrogen Production

“…Attachment of the ruthenium complex to NiRd was provided through a native free cysteine residue, close to the metal-binding site. The effective distance between the nickel center and the photosensitizer was modulated Inspired by the nickel center of [NiFe]-hydrogenases, Chackraborty and coworkers recently developed artificial metalloenzymes by engineering a tetrathiolate nickel center (NiS 4 ) into de novo designed coiled coils [244,245]. In their first study, self-assembly of two de novo peptides, each bearing a CXXC motif, in the presence of nickel(II) yielded a two-stranded coiled coil (2SCC) enclosing the NiS 4 site (Figure 10b and Table 2, entry 38) [244].…”

“…Spectroscopic studied revealed that a precise acidity is required for activity, suggesting that the protonation state of Cys is crucial for H 2 production. In the latest study, a peptide sequence was designed to favor a four-stranded coiled coil (4SCC), and the presence of a rubredoxin-like CXXC motif in each peptide strand was conceived to provide a dual nickel-binding site (Table 2, entry 39) [245]. Interestingly, nickel binding induced an oligomerization shift, stabilizing the formation of dimers, while the apo form was predominantly trimeric.…”