Designed Rubredoxin miniature in a fully artificial electron chain triggered by visible light

Abstract

Designing metal sites into de novo proteins has significantly improved, recently. However, identifying the minimal coordination spheres, able to encompass the necessary information for metal binding and activity, still represents a big challenge, today. Here, we tested our understanding with a benchmark, nevertheless difficult, case. We assembled in a small 28-residue peptide the quintessential elements required to correctly fold around a single iron redox center, coordinated to four cysteinyl thiolates (FeCys4 site), and to efficiently function in electron-transfer. This study represents a milestone in de novo protein design: for the first time the crystal structure of a designed tetra-thiolate metal-binding protein is reported within sub-Å agreement with the intended design. This allowed us to well correlate structure to spectroscopic and electrochemical properties. Given its high reduction potential compared to natural and designed FeCys4-containing proteins, we exploited it as terminal electron acceptor of a fully artificial chain triggered by visible light.

Designed Rubredoxin miniature in a fully artificial electron chain triggered by visible light

“…The crystal structure of ZnMETPsc1 complex has been deposited in wwPDB with the accession code 5SBG 66 . The experimental and computational source data used in this study are available in the Supplementary Information and in the Zenodo database under accession code 7748883 67 .…”

“…The custom codes used are available in the supplementary information file and in a Zenodo repository under accession code 7748883 67 .…”

Differences in heavy metal binding to cysteine‐containing coiled‐coil peptides

“…However, it should be noted that Zn(II) does indeed bind to designed, non-coiled-coil, peptides containing only Cys ligands. 24,25 For CX3C, Pb(II), Hg(II) and Cd(II), all resulted in an increase in the intensity of the CD signal, and an increase in helicity, with helicity increasing in the order Pb(II) < Hg(II) < Cd(II) (Table 2). This order is likely to be due to the relative size of the metal ions; Pb(II) is the largest at 119 pm with Hg(II) and Cd(II) being 109 and 102 pm, respectively.…”