Generation and isolation of recombinant retinoid oxidoreductase complex.

All-trans-retinoic acid (RA) is a bioactive lipid that influences many processes in embryonic and adult tissues. Given its bioactive nature, cellular concentrations of this molecule are highly regulated. The oxidation of all-trans-retinol to all-trans-retinaldehyde represents the first and rate-limiting step of the RA synthesis pathway. As such, it is the target of mechanisms that fine-tune RA levels within the cell. RDH10 is one enzyme responsible for the oxidation of all-trans-retinol to all-trans-retinaldehyde, and together with the all-trans-retinaldehyde reductase DHRS3 forms an oligomeric protein complex. The resulting retinoid oxidoreductase complex (ROC) is bifunctional and has the capacity to regulate steady-state levels of the direct precursor of RA, all-trans-retinaldehyde. As ROC represents a major regulatory element within the RA synthesis pathway, it is essential that methods are in place that allow for the study of this complex. Here we describe the production and isolation of recombinant ROC using a baculovirus expression system. Recombinant proteins retain enzymatic activities in intact microsomes and can be affinity purified for analysis. These methods can be used to assist in the assessment of ROC properties and the regulation of this protein complex's functional attributes.