Native Protein Template Assisted Synthesis of Non-Native Metal-Sulfur Clusters

Abstract

Metalloenzymes are the most proficient nature catalysts that are responsible for diverse biochemical transformations introducing excellent selectivity and performing at high rates, using intricate mutual relationships between metal ions and proteins. Inspired by nature, chemists started using naturally occurring proteins as templates to harbor non-native metal catalysts for the sustainable synthesis of molecules for pharmaceutical, biotechnological and industrial purposes. Therefore, metalloenzymes are the relevant targets for the design of artificial biocatalysts. The search and development of new scaffolds capable of hosting metals with high levels of selectivity could significantly expand the scope of bio-catalysis. To meet this challenge, herein, three native scaffolds: [1Fe-4Cys] (rubredoxin), [3Fe-4S] (ferredoxin), and [S2MoS2CuS2MoS2]-ORP (orange protein) protein scaffolds are case studies describing templates for the synthesis of non-native monomeric to mixed metal–sulfur clusters, which mimic native Ni containing metalloenzymes including [Ni-Fe] Hydrogenase and [Ni-Fe] CO Dehydrogenase. The non-native metal-substituted metalloproteins are not only useful for catalysis but also as spectroscopic probes.

Molybdenum‐Copper Antagonism In Metalloenzymes And Anti‐Copper Therapy

“…The scaffold of apo-ORP was also used to promote the protein-assisted formation of protein derivatives harboring heterometallic clusters, [S 2 MoS 2 MS 2 MoS 2 ] 3À /2À (M = copper (native metal), iron, cobalt, nickel, or cadmium (nonnative metals). [18,19,68] The "ATCUN" motif (amino-terminal copper and nickel binding site). [70] was inserted into the ORP at the N-terminus for understanding the Mo/CuÀ cluster assembly in vivo in the metalcofactor binding pocket (Figure 4A).…”

“…Therefore, it is difficult to identify the exact binding region in the polypeptide chain. To overcome this, we have synthesized EPR or NMR active ORP metal derivatives by replacing the native copper ion with non-native metal ions like iron, cobalt, nickel, and cadmium ions, [15][16][17] or coordinating, at Cu-site, small organic thiol or fluorinated-thiol ligands ( 1 H or 19 F NMR) [15][16][17] (Figure 5). We attempted to reconstitute the apo-ORP with a synthesized semi-structural model compound with thiol derivatives, [15][16][17] but these model compounds have low solubility and stability in biological buffers.…”

“…The apo‐ORP is reconstituted with CuCl 2 and TTM to yield holo‐ORP. The scaffold of apo‐ORP was also used to promote the protein‐assisted formation of protein derivatives harboring heterometallic clusters, [S 2 MoS 2 MS 2 MoS 2 ] 3−/2− (M=copper (native metal), iron, cobalt, nickel, or cadmium (non‐native metals) [18,19,68] …”

“…The first inorganic model of ORP was reported by Maiti et al in 2004. [15] As both Mo and Cu are EPR silent and there is no suitable NMR reporter, more Mo/Cu derivatives were also synthesized as NMR and EPR probes [16][17][18][19] for finding the exact location in the protein cavity, but these probes failed to give fruitful results.…”