The production of the ostrich NH2-terminal POMC fragment requires cleavage at a unique signal peptidase site.
The NH2-terminal fragment of ostrich proopiomelanocortin was isolated and purified following acid/acetone extraction. The amino acid sequence was deduced by automatic Edman degradation of the native as well as CNBr-, tryptic-, and S. aureus protease-derived peptides. Primary structure analysis reveals its close resemblance to other known sequences, especially to amphibian POMC. The usual Trp/Gln-Cys NH2-terminal sequence found in all other homologous sequences, is replaced here by an His-Gly-Pro-Cys sequence. In addition, the gamma-MSH sequence, contrary to salmon POMC, is present and contains three substitutions, namely a Ser, an Asn, and a Lys residue substituting the normally occurring mammalian Gly, Asp, and Arg residue, respectively. Finally, the molecular weight of this fragment as deduced from ion-spray mass spectrometry and sedimentation equilibrium centrifugation is in close agreement with the proposed structure.
Naudé
R J
RJ
Biochemistry Department, University of Port Elizabeth, Republic of South Africa.
Litthauer
D
D
Oelofsen
W
W
Chrétien
M
M
Lazure
C
C
D000595:Amino Acid Sequence; D000818:Animals; D001717:Birds / Q000378:metabolism*; D010450:Endopeptidases / Q000378:metabolism*; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000378:metabolism*; D011333:Pro-Opiomelanocortin / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases
D008565:Membrane Proteins; D010446:Peptide Fragments; D011333:Pro-Opiomelanocortin; D010450:Endopeptidases; D012697:Serine Endopeptidases; C026515:type I signal peptidase