Nine heme cytochrome c (9Hcc) is a monomeric multi‐heme cytochrome c found in the sulfate‐reducing bacteria of Desulfovibrio desulfuricans (Dd) ATCC 27774 and Desulfovibrio desulfuricans Essex 6. The polypeptide chain comprises 296 residues and wraps around nine hemes of type‐c that bind the polypeptide chain through thioether bridges to cysteine residues. This represents the first known structure of a multi‐heme cytochrome where copies of a tetra‐heme cytochrome c 3 ‐like fold are present in the same polypeptide chain. The high homology between 9Hcc and the C‐terminal region of Desulfovibrio vulgaris Hildenborough (DvH) Hmc, as well as the presence of the 9Hcc gene within an operon similar to that of the DvH Hmc, strongly support the proposal that 9Hcc is the high‐molecular‐weight cytochrome of Dd. Several in vitro studies, as well as our crystallographic and modeling studies suggest that cytochrome c 3 is the mediator between the [NiFe] hydrogenase and 9Hcc in Dd.
Tetraheme cytochromes c 3 constitute the best‐studied group among the multiheme cytochromes belonging to the class III of Ambler's classification. Since 1954, when cytochrome c 3 was isolated from Desulfovibrio vulgaris for the first time by Postgate, these proteins have been widely characterized, especially those from the Desulfovibrio ( D .) genus. All these cytochromes have their heme group attached to the polypeptide chain by cysteine residues and show bis‐histidinyl coordination of the heme iron and a highly conserved heme‐binding motif (CXXCH or CXXXXCH). Cytochromes c 3 show a wide variety of redox potentials, ranging from 0 to −400 mV, are usually periplasmatic proteins, and are believed to play key roles in the electron transfer chains. Recently, the cytochrome c 3 group was divided into two main types on the basis of structural, functional, and genetic differences: type I cytochrome c 3 (TpI‐ c 3 ) and type II cytochrome c 3 (TpII‐ c 3 ). This paper reviews their structural, spectroscopic, and functional properties, based on the wealth of information currently available. These include physicochemical properties, redox mechanisms, coupling between electron and proton transfer, and data concerning the interaction with their redox partners obtained by experimental and molecular modeling methods.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
334 Leonard St
Brooklyn, NY 11211
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.