THE BILIN-BINDING PROTEIN OF PIERIS-BRASSICAE - CDNA SEQUENCE AND REGULATION OF EXPRESSION REVEAL DISTINCT FEATURES OF THIS INSECT PIGMENT-PROTEIN

The bilin-binding protein (BBP) is a blue pigment protein which is abu ndant in the butterfly Pieris brassicae. In an attempt to clarify the physiological role of this member of the lipocalin family of proteins, its complete cDNA was cloned and expression of the BBP gene in P. bra ssicae was investigated. It was found that synthesis of the BBP mRNA i s highly regulated during the insect's ontogenesis. In larvae after th e third ecdysis as well as in pupae and adults, large amounts of the m RNA are present. Each of these stages itself displays a distinct time course of mRNA synthesis. In addition, BBP is expressed tissue specifi cally, with the fat body being the major source of this secretory prot ein in the larvae. Hence, the expression pattern of BBP in this organi sm is markedly different from the closely related pigment protein inse cticyanin in Manduca sexta. Finally, the bacterial expression of BBP i n a functional state was established as a basis for the future analysi s of its ligand-binding functions by protein engineering.