Team:CityU HK/project/module fad

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FadD & FadL Module

The ultimate goal of our project is to genetically engineer an E. coli strain to increase its fatty acid uptake efficiency and ability to convert the absorbed fatty acid into α-linolenic acid (ALA).

In order to achieve this, we have sub-divided our project into three parts:
a. Enhanced uptake of long chain fatty acids (LCFAs) by E. coli
b. Increased conversion of fatty acyl-CoA into free fatty acid
c. Enhanced conversion of free fatty acid into ALA

The uptake of exogenous long chain fatty acids is controlled by the fadL and fadD genes.


Figure 1. Importation of long-chain fatty acids by FadL and FadD. Long chain fatty acids (LCFAs) in the extracellular space are imported by the action of FadL protein into the periplasmic space. Due to the low pH, LCFAs are are protonated. FadD adds a CoA moiety to the carboxyl group, which facilitates the transport of LCFAs into the cytosol.


The fadL gene codes for an outer membrane-bound fatty acids transport protein that facilitates the import of long chain fatty acids into the periplasmic space where they are protonated and then partitioned at the inner membrane (with the ionic head pointing towards the periplasmic space). Protonated fatty acids are unable to pass through the inner membrane into the cytosol and require the assistance of the FadD protein. The fadD gene codes for an inner membrane-associated long chain acyl-CoA synthetase enzyme in E. coli, which catalyses the addition of a CoA moiety to the fatty acids and their subsequent transport across the inner membrane into the cytosol. FadD is therefore required both for the transport of LCFAs through the inner membrane into the cytosol and their activation for metabolism via the β-oxidation pathway. By overexpressing FadL and FadD, we aim to enhance LCFA uptake to boost the subsequent conversion of fatty acyl-CoA to ALA.


References:

James D. Weimar, Concetta C. DiRusso, Raymond Delio and Paul N. Black (August 16, 2002). Functional Role of Fatty Acyl-Coenzyme A Synthetase in the Transmembrane Movement and Activation of Exogenous Long-chain Fatty Acids. The Journal of Biological Chemistry, 277(33), 29369-29376.

Wikipedia. (n.d.). Fatty acid. Retrieved October 16, 2014, from http://en.wikipedia.org/wiki/Fatty_acid

Feske, S. (September 2007). Calcium signalling in lymphocyte activation and disease. Nature Reviews Immunology, 7(9), 690-702.



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