photoprotection. They are typically solubilized in membranes or attached to proteins. In cyanobacteria, the
photoactive soluble Orange Carotenoid Protein (OCP) is involved in photoprotective mechanisms as a
highly active singlet oxygen and excitation energy quencher. Here we describe a method for producing large
amounts of holo-OCP in E.coli. The six different genes involved in the synthesis of holo-OCP were
introduced into E. coli using three different plasmids. The choice of promoters and the order of gene
induction were important: the induction of genes involved in carotenoid synthesis must precede the
induction of the ocp gene in order to obtain holo-OCPs. Active holo-OCPs with primary structures derived
from several cyanobacterial strains and containing different carotenoids were isolated. This approach for
rapid heterologous synthesis of large quantities of carotenoproteins is a fundamental advance in the
production of antioxidants of great interest to the pharmaceutical and cosmetic industries.