Cysteine Linkages Accelerate Electron Flow through Tetra-Heme Protein STC

Researchers from the Thomas Young Centre and the Institute for Advanced Study, Technische Universität München in Germany have made important findings in multi-heme proteins, by combining state-of-the-art quantum mechanics and and molecular dynamics calculations.  This paper was published in the Journal of the American Chemical Society

Xiuyun Jiang, Zdenek Futera, Md. Ehesan Ali, Fruzsina Gajdos, Guido F. von Rudorff, Antoine Carof, Marian Breuer, and Jochen Blumberger

Multi-heme proteins have emerged as a new category of conductive materials for potetially revolutionizing bionanotechnological advances such as electronic communication, signaling and sensing with bacterial cells, non-toxic implantable bioelectronics devices or even artificial skin.  However, some of their most important properties, such as heme-to-heme electron transfer (ET) rate constants and the protein-limited electron flux through these structures have eluded experimental determination so far.  Here we compute these properties for a representative tetra-heme protein (STC) by combining state-of-the-art quantum chemical and molecular dynamics calculations.  Unexpectedly, we find that cysteine linkages inserting in the space between the heme cofactors accelerate ET rates and the total electron flow through this protein by a factor of approximately 50.

This finding has three important implications (i) the rate accelerating effect due to cysteines allws multiheme proteins to use hem-hem orientation that are suboptimal in terms of cunduction without sacrificing much ET speed, thereby shining light on an important design principle of these proteins (ii) it challenges the traditional view that biological ET rates are determined solely by heme-to-heme edge distances (Moser et al. PNAS 111,614 (2014)).  (iii) Moreover, there is currently a strong effort to experimentally determine heme-to-heme ET rates in these proteins making our predictions very timely.


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