Structurally different rat liver medium-chain acyl CoA dehydrogenases directed by complementary DNAs differing in...

Area of Science:

• Biochemistry
• Molecular Biology
• Enzymology

Background:

• Medium-chain acyl CoA dehydrogenase (MCAD) is crucial for fatty acid metabolism in the liver.
• Understanding MCAD structure-function relationships is vital for metabolic research.
• Expression of functional enzymes in microbial systems facilitates biochemical studies.

Purpose of the Study:

• To investigate the impact of different 5'-cDNA regions on rat liver MCAD expression in E. coli.
• To characterize the enzymatic activity and FAD binding of MCAD variants.
• To elucidate the role of the leader peptide and N-terminus in MCAD function.

Main Methods:

• Recombinant expression of rat liver MCAD variants in Escherichia coli using various plasmids.
• Protein extraction, purification, and homogeneity assessment.
• Enzymatic activity assays and FAD content determination.

Main Results:

• A 44 kDa MCAD protein expressed from pRMCADm-3 exhibited high activity and purified to homogeneity with bound FAD.
• A 45 kDa MCAD protein from pRMCADm-1 lacked FAD and activity, indicating leader peptide interference with FAD binding.
• A 40 kDa MCAD protein from pRMCADm-6 also lacked FAD, suggesting N-terminal deletions impair FAD association.

Conclusions:

• The leader peptide of rat liver MCAD significantly hinders FAD binding.
• N-terminal deletions in the MCAD apoprotein can also compromise FAD association.
• Recombinant expression systems are effective for studying MCAD structure-function relationships and FAD cofactor interactions.