Issue 15, 2018

Using porphyrin–amino acid pairs to model the electrochemistry of heme proteins: experimental and theoretical investigations

Abstract

Quasi reversibility in electrochemical cycling between different oxidation states of iron is an often seen characteristic of iron containing heme proteins that bind dioxygen. Surprisingly, the system becomes fully reversible in the bare iron–porphyrin complex: hemin. This leads to the speculation that the polypeptide bulk (globin) around the iron–porphyrin active site in these heme proteins is probably responsible for the electrochemical quasi reversibility. To understand the effect of such polypeptide bulk on iron–porphyrin, we study the interaction of specific amino acids with the hemin center in solution. We choose three representative amino acids–histidine (a well-known iron coordinator in bio-inorganic systems), tryptophan (a well-known fluoroprobe for proteins), and cysteine (a redox-active organic molecule). The interactions of these amino acids with hemin are studied using electrochemistry, spectroscopy, and density functional theory. The results indicate that among these three, the interaction of histidine with the iron center is strongest. Further, histidine maintains the electrochemical reversibility of iron. On the other hand, tryptophan and cysteine interact weakly with the iron center but disturb the electrochemical reversibility by contributing their own redox active processes to the system. Put together, this study attempts to understand the molecular interactions that can control electrochemical reversibility in heme proteins. The results obtained here from the three representative amino acids can be scaled up to build a heme–amino acid interaction database that may predict the electrochemical properties of any protein with a defined polypeptide sequence.

Graphical abstract: Using porphyrin–amino acid pairs to model the electrochemistry of heme proteins: experimental and theoretical investigations

Supplementary files

Article information

Article type
Paper
Submitted
27 Jan 2018
Accepted
19 Mar 2018
First published
19 Mar 2018

Phys. Chem. Chem. Phys., 2018,20, 10018-10029

Using porphyrin–amino acid pairs to model the electrochemistry of heme proteins: experimental and theoretical investigations

R. N. Samajdar, D. Manogaran, S. Yashonath and A. J. Bhattacharyya, Phys. Chem. Chem. Phys., 2018, 20, 10018 DOI: 10.1039/C8CP00605A

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements