Structures of short-lived physiological electron transfer complexes

Lead Research Organisation: University of Manchester
Department Name: Life Sciences

Abstract

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Technical Summary

Weakly associated physiological electron transfer (eT) complexes have remained elusive to structural studies. Our work targets understanding of the structural elements of complex formation between redox proteins that undergo large-scale conformational change as a prerequisite to complex assembly, using the ETF proteins as paradigm model systems. The ETFs are highly mobile proteins that interact with a number of key primary dehydrogenases, complexes for which we seek high-resolution structures. Our work will provide atomic insight into a new robust engineering principle for interprotein electron transfer, allowing for specific recognition of multiple redox partners, whilst maintaining efficient electron transfer rates. This will have general implications for physiological, protein-mediated electron transfer.
 
Description Living organisms convert energy obtained from diverse sources (e.g. food, light) into motion, heat, high-energy compounds etc. A large proportion of these life-sustaining energy convertions occur by transferring electrons along a series of electron-carriers, a process that bears analogy to our use of electricity in modern-day life. Enzymes can obtained high-energy electrons from substrates and pass these on to distinct molecules. This research focusses on one particular molecule called electron transferring flavoprotein (ETF), a protein that is essential to the electric circuitry of the cell. Suprisingly, this particular protein displays a certain level of promiscuity (e.g. it will interact with several enzymes), but also specificity (e.g. it will only interact with a certain subset of enzymes). How these two inherently opposite trends are reconciled at the molecular level is the major question we wished to address in this research. Our work has revealed that ETF is a highly dynamic molecule that contains distinct elements, the business element that contains a flavin co-factor (the chemical group that carries electrons) as well as a protein:protein interaction module which is distinct from the flavin-domain. This molecular structure explains how ETF can reconcile specificity (conferred by the protein:protein interaction domain) with promiscuity (underpinned by the mobility of the flavin-domain). The mobility of the flavin domain is key to the nature of the protein:protein complexes made between ETF and its partners, and we have established the atomic structure of both the human ETF:MCADH (medium chain Acyl-CoA dehydrogenase, an enzyme involved in fatty acid breakdown) and bacterial ETF:TMADH (trimethylamine dehydrogenase, an enzyme involved in amine oxidation). In each case, the mobile flavin-domain seeks out those conformations that are compatible with electron transfer, while the remainder of the ETF molecule serves to anchor ETF onto the protein partner surface. This intricate protein:protein contact can however not be long-lived, as ETF is required to pass electron on to the next element in the cell-circuitry. To enhance the flux of electrons, ETF contains elements that stabilise the "off" rather than "on" conformation of the flavin-domain, leading to rapid turnover of the protein:protein complex. Our research has shown how Nature can use mobile cofactor carrying domains incorporated in a modular molecular design to transfer electrons from one molecule to another.
Exploitation Route This new model for electron transfer can be used in future design and/or understanding of applications that make use of redox enzymes, such as biosensors using electrodes/enzyme interface.
Sectors Chemicals,Energy,Environment
URL http://www.ncbi.nlm.nih.gov/pubmed/15582386
 
Description Big Bang national competition, senior judge 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Schools
Results and Impact Stimulated 16-18 years to keep engaged with science and pursue a career in this field.

No direct impact
Year(s) Of Engagement Activity 2010,2011,2012,2013,2014
URL http://www.nsecuk.org/
 
Description MIB open day 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact Questions and discussions with GCSE student of regional area.

Possibly more applicants to Manchester uni of local/regional schools in the biochemistry area.
Year(s) Of Engagement Activity 2012,2013,2014
 
Description Media interest, synthetic biology in METRO 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Media (as a channel to the public)
Results and Impact No immediate results.

I have had more applicants to PhD positions as well as some request for summer placements in our lab following this.
Year(s) Of Engagement Activity 2010
URL https://royalsociety.org/news/metro/synthetic-biology/
 
Description Member of the judging team for Local Heroes, Extending the Reach awards from the Royal Society 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact Decisions made on awards
Year(s) Of Engagement Activity 2010
 
Description School visit, primary school in Nantwich 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact Discussion on how to engage early school children in science

No direct notable impacts
Year(s) Of Engagement Activity 2010