THE MOLECULAR CHARACTERIZATION OF CHICKEN PITUITARY N-TERMINAL PROOPIOMELANOCORTIN (POMC)

Monoclonal antibodies (Mabs) specifically recognizing the chicken pitu itary corticotropes were used to isolate a population of closely relat ed peptides from crude chicken pituitary extracts. A homogeneous N-ter minal sequence homologous to the extreme N-terminus of mammalian and a mphibian pro-opiomelanocortin (POMC) was revealed. Further physicochem ical analysis proved the existence of a series of C-terminally truncat ed peptides including 3 major molecular species corresponding to Ser1- Gly64, Ser1-Arg73 and Ser1-Gly105 respectively. The two latter molecul es were shown to be N-glycosylated at position Asn67, with mass spectr ometric data indicating a carbohydrate structure of the oligomannose 5 type, in addition to two more complex structures. No evidence was fou nd in favour of O-glycosylation on Ser47. Degenerated PCR primers were deduced from the above protein sequence and from the known chicken ad renocorticotropic hormone (ACTH) sequence. The nucleotide sequence obt ained by reversed transcription PCR (RT-PCR) completely confirmed the new amino acid sequence data including pro-gamma-MSH, the joining pept ide and ACTH. (C) 1998 Elsevier Science Ireland Ltd. All rights reserv ed.