Abstract
We investigated the association of two model primordial polypeptides, each bearing an ancient and ubiquitous phosphate-binding motif, with DNA. The association rate and the amount of bound DNA relates to the electron spin-dependent polarizability of the binding protein. The spin-dependence is a result of the chirality of the proteins and is a consequence of the chiral-induced spin selectivity (CISS). We show correlation between the spin dependence and the handedness of the chiral protein. Since the polypeptides studied are hypothesized to be among the initial stand-alone ‘seed’ fragments from which contemporary protein domains evolved, the results suggest the importance of spin-dependent polarizability early in protein evolution. We provide model calculations clarifying the underlying reasons for spin selectivity and estimating its impact on protein function.
Significance statement All biomolecular interactions involve charge reorganization due to the displacement of electrons upon binding. In past studies it was established that the charge reorganization in chiral molecules is accompanied by electrons’ spin polarization. Which spin is displaced depends on the handedness of the chiral system. This phenomenon was extensively studies as part of the chiral-induced spin selectivity (CISS) effect. Here, we demonstrate that the CISS effect is operative in ancient nucleic acid-binding domains that remain ubiquitous in contemporary proteins. We demonstrate that the greater the spin-polarizability of primitive proteins, the more efficient is the charge reorganization and consequently stronger and faster is the DNA binding. The CISS effect could have supported the kinetic stability of primitive biomolecular complexes, contributing to the emergence of homochirality in biological systems.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
This version contains further discussion of the model and simulations shown in Figure 6.
