Pituitary immunoreactive γ-melanotropins are glycosylated oligopeptides

Abstract

Nakanishi et al.1 have recently characterised the complete sequence of the mRNA isolated from the intermediate lobe of bovine pituitary which codes for the 31,000 molecular weight (31 K) precursor protein of corticotropin/β-lipotropin (ACTH/β-LPH). The corresponding amino acid sequence translated from this mRNA revealed in the cryptic region of the precursor protein a fragment sharing a common amino acid sequence with the α- β-melanotropins (α-MSH, β-MSH) and thus named γ-MSH1. To study whether this γ-MSH fragment is also processed and released as a biologically active substance and to ascertain its location in the pituitary and possibly in the brain, we have raised antibodies to the synthetic replicate of γ3-MSH (ref. 2). We report here the detection of at least two γ-MSH-like peptides in the pituitary using these antibodies in a radioimmunoassay (RIA) and, furthermore, evidence that these two peptides are glycosylated.