Award details

The assembly of mitochondrial c-type cytochromes by System III

Reference	BB/H017887/1
Principal Investigator / Supervisor	Professor Stuart John Ferguson
Co-Investigators / Co-Supervisors	Dr Julie Stevens
Institution	University of Oxford
Department	Biochemistry
Funding type	Research
Value (£)	371,575
Status	Completed
Type	Research Grant
Start date	01/10/2010
End date	30/04/2014
Duration	43 months

Abstract

A post-translational reaction adds heme to the sulfurs of two cysteines in a CXXCH motif of c-type cytochromes. In the mitochondria of many, including human, but not all, eukaryotic cells this attachment is catalysed by heme lyase enzymes. Next to nothing is known about the functioning of these essential proteins; mitochondrial are non-functional without cytochrome c. We wish to identify what is recognised on the target apocytochrome c by the lyase; there is specificity as highly related prokaryotic cytochromes are not recognised whereas the prokaryotic system for making cytochromes c recognises only the CXXCH motif. There are putative target sequences on the apo cytochrome which will be investigated by mutagenesis using an in vivo expression system for the heme lyase and cytochrome c. Similarly we shall investigate the roles of conserved residues in the lyase itself. We aim to develop an in vitro system for studying the heme lyase so as to analyse its enzymology and proceed towards investigation by the methods of structural biology.

Summary

Proteins are complex biomolecules that are essential to the structure and function of all living cells. In order to diversify their functions, proteins use additional molecules called cofactors, of which there are many types. Heme is one such cofactor; it is an organic chemical with an iron atom in the centre and has many essential functions in different cellular processes. Many proteins that contain heme undergo a process after they are made in the cell in which bonds are formed between the protein and the heme; these are called cytochromes c and are essential in respiration and in reactions that involve the transfer of electrons. In animal cells there are two c-type cytochrome molecules which are both found in the mitochondria. These cytochromes play a key role underpinning the mitochondrion's role as the powerhouse of the cell. Additionally, one of these cytochromes c can be released from the mitochondrion under certain conditions as a trigger for the process of programmed cell death. In other cases, heme associates with proteins without forming bonds with them, for example in hemoglobin, which uses the heme to bind oxygen in blood. In the case where the heme cofactor becomes bonded to the cytochrome, other proteins are needed to assist in this reaction, which is not spontaneous. In animals a single protein speeds up the covalent attachment of heme to protein to give a cytochrome c. Our proposed research seeks to understand how this protein functions, using a variety of experimental approaches and techniques. It is also important to understand the process of making cytochromes c as a fundamental and central biological process, in order to complete a description of the essential biochemical reactions that constitute life.

Impact Summary

The impact will inevitably depend on the outcome of the work and so at this stage it is simply not possible to identify non-academic beneficiaries. There are disease states associated with defects in the proteins to be studied and therefore we will towards the end of the grant period produce a overview review article suitable for the medical literature. We will take advantage of the new Departmental web site to publicise the work and be in touch with the University's development organisation, ISIS, if we see commerical opportunities developing. We will interact with the schools sector both by making visits and being willing to host pupils for work experience.

Committee	Research Committee D (Molecules, cells and industrial biotechnology)
Research Topics	Structural Biology
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	X – not Funded via a specific Funding Scheme

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