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This Sandbox is Reserved from January 10, 2010, through April 10, 2011 for use in BCMB 307-Proteins course taught by Andrea Gorrell at the University of Northern British Columbia, Prince George, BC, Canada.

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spinqualitylabelsall models PDB ID 3cp5 Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image
3cp5, resolution 1.24Å ()
Ligands:	,
Gene:	cytC (Rhodothermus marinus)
Structural annotation: Resources: UniProt : B3FQS5
Evolutionary conservation: Toggle Conservation Colors: Rows = identical sequences: Further Information: Caveats, Explanation, Complete Results at ConSurfDB
Resources:	FirstGlance, OCA, PDBsum, RCSB
Coordinates:	save as pdb, mmCIF, xml

Cytochrome c (cyt c) is a superfamily of proteins belonging to the class of all-α proteins with a core of helices and a covalently-bound heme prosthetic group.^[1][2] The cytochrome c superfamily contains many different families including monodomain and multi-domain C-type cytochromes (ex. cyt c4, a diheme C-type cytochrome, and NrfB, a pentaheme C-type cytochrome). This page focuses mainly on the cytochrome c superfamily, briefly discussing various types within the superfamily. The monoheme cytochrome c purified from Rhodothermus marinus will be discussed in greater detail than other C-type cytochromes.

Contents 1 Introduction 1.1 Rhodothermus marinus 2 Structure 3 Mechanism 4 Importance 5 References

Introduction

Cytochromes are a class of heme-containing proteins that are generally membrane-bound. They are soluble proteins^[2] found in bacteria and the mitochondria of eukaryotic organisms, and are known as respiratory pigments because they are involved in electron transfer in various electron transport chains.^[3] Cytochromes can be categorized into three different types, all based on the type of prosthetic heme group the cytochrome contains. Cytochrome c is named such because it contains the heme c, which is distinguished from hemes a, b, and d by its coordination to the protein scaffold by cysteinyl residues.^[3]

Cyt c has been split into four classes^[4], Class I containing single domain C-type cytochromes of which there has been at least six classes found in prokaryotes such as Desulfovibrio desulfuricans, Rhodospirillum rubrum, and Rhodothermus marinus.

Rhodothermus marinus

Rhodothermus marinus is a Gram-negative bacterium in the class Sphingobacteria, in phylum Bacteroidetes. These bacteria are thermophilic, obligate aerobes that have been previously isolated from shallow-water submarine hot springs located in Iceland.^[5] A monoheme cytochrome c that has been thought to be the first member of a new class of cyt c was recently purified from R. marinus, having the nomenclature Rmcytc.^[2]

Structure

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All members in the C-type cytochrome superfamily contain a heme prosthetic group that is covalently attached to the protein via two thioether bonds to cysteine residues; most cytochromes c occur in a , where a histidine residue is one of the two axial ligands of the heme iron.^[2][3] The other axial position, in monoheme cytochromes c, may be left vacant or be occupied by histidine or methionine residues, but can sometimes be occupied by cysteine or leucine residues.^[2]. The typical monoheme cyt c fold is formed by helices . In Rmcytc there are seven α-helices that are folded around the porphyrin ring, all connected by random coils.^[2]

In Rmcytc, the porphyrin ring is axially coordinated by

Monoheme cytochromes c are involved in electron transport chains in both prokaryotes and eukaryotic mitochondria.^[2] They mediate the transfer of electrons mainly from the bc₁ complexes, or their analogs, in the electron transport chain to heme-copper oxygen reductases (HCOs) during oxidative phosphorylation. Heme c containing domains are often found fused to other protein domains such as these HCOs, including the caa₃ oxygen reductases^[2][6]; these enzymes are membrane-bound and catalyze the reduction of O₂ to water.^[7] In addition to being involved in the electron transport systems in oxidative phosphorylation, monoheme cyt c has also been seen to participate in the electron transport chain of photosynthesis.^[2]

Mechanism

Importance

References

1. ↑ Gough J, Karplus K, Hughey R, Chothia C. Assignment of homology to genome sequences using a library of hidden Markov models that represent all proteins of known structure. J Mol Biol. 2001 Nov 2;313(4):903-19. PMID:11697912 doi:10.1006/jmbi.2001.5080
2. ↑ ^{2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8} Stelter M, Melo AM, Pereira MM, Gomes CM, Hreggvidsson GO, Hjorleifsdottir S, Saraiva LM, Teixeira M, Archer M. A Novel Type of Monoheme Cytochrome c: Biochemical and Structural Characterization at 1.23 A Resolution of Rhodothermus marinus Cytochrome c. Biochemistry. 2008 Oct 15. PMID:18855424 doi:10.1021/bi800999g
3. ↑ ^{3.0 3.1 3.2} Reedy CJ, Gibney BR. Heme protein assemblies. Chem Rev. 2004 Feb;104(2):617-49. PMID:14871137 doi:10.1021/cr0206115
4. ↑ Ambler RP. Sequence variability in bacterial cytochromes c. Biochim Biophys Acta. 1991 May 23;1058(1):42-7. PMID:1646017
5. ↑ Alfredsson GA, Kristjansson JK, Hjörleifsdottir S, Stetter, KO. Rhodothermus marinus, gen. nov., sp. nov., a thermophilic, halophilic bacterium from submarine hot springs in Iceland. J Gen Microbiol. 1988 Feb;134(2):299-306.
6. ↑ Soares CM, Baptista AM, Pereira MM, Teixeira M. Investigation of protonatable residues in Rhodothermus marinus caa3 haem-copper oxygen reductase: comparison with Paracoccus denitrificans aa3 haem-copper oxygen reductase. J Biol Inorg Chem. 2004 Mar;9(2):124-34. Epub 2003 Dec 23. PMID:14691678 doi:10.1007/s00775-003-0509-9
7. ↑ Pereira MM, Santana M, Teixeira M. A novel scenario for the evolution of haem-copper oxygen reductases. Biochim Biophys Acta. 2001 Jun 1;1505(2-3):185-208. PMID:11334784