Molecular cloning of propiomelanocortin cDNA and multi-tissue mRNA expression in Parasilurus asotus

Abstract

We investigated the structure,evolution,and tissue specific expression of Parasilurus asotus proopiomelanocortin(POMC) cDNA using RT-PCR and RACE.The POMC cDNA was 1 099 bp in length and contained a 129 bp 5′UTR,a 322 bp 3′UTR,and a 648 bp open reading frame encoding a protein of 215 amino acids.The catfish POMC protein contained a signal peptide(SP,Met1-Ala28),an N-terminal peptide(Gln29-Asp102),adrenocorticotropic hormone(ACTH,Ser105-Met144),α-melanocyte stimulating hormone(α-MSH,Ser105-Val117),corticotropin-like intermediate lobe peptide(CLIP,Arg123–Met144),β-lipotropin(β-LPH,Glu145-Ser158),β-MSH(Asp161-Ser177),and β-Endorphin(β-EP,Tyr178-Leu215).Catfish POMC protein does not contain a γ-MSH region and the majority of the joining peptide and part of the γ-LPH were deleted.The protein shared the highest similarity(88%) with channel catfish(Parasilurus asotus) POMC.The most highly conserved active peptide was α-MSH,followed by β-MSH,β-EP,and CLIP whereas γ-MSH,joining peptide(JP),and γ-LPH were located in the most divergent region.The protein had a calculated molecular weight of 24.66 kD,a theoreti-cal isoelectric point of 7.25,was hydrophilic in most regions,and was rich in B cell antigenicity positions.Catfish POMC mRNA was primarily expressed in the pituitary and the concentration of mRNA was much higher in brain than in other tissues.