title: Lungfish prolactin exhibits close tetrapod relationships.
abstract: This paper describes the isolation and the complete amino-acid sequence of prolactin (PRL) from the pituitary glands of African lungfish, Protoputerus aethiopicus. We purified the hormone from an alkaline extract of the pituitaries using a two-step chromatographic procedure by detecting specific immunoblot reactivity with rabbit antisera against salmon PRL. The lungfish PRL consists of 200 amino-acid residues. Sequence comparison revealed that the PRL shows 66% identities with amphibian, reptilian and bird PRLs, 57% with mammalian PRLs, and 38% with teleost (modern bony fish) PRLs. Moreover, the PRL contains three disulfide bonds homologous to those of tetrapod PRLs and differs from teleost PRLs which lack the amino-terminal disulfide bond. Thus, the structural features of lungfish PRL indicate a closer relationship to tetrapod PRLs than to teleost PRLs. All PRLs sequenced to date share 22 common amino acids, which may be important for the activities common to all PRLs.
authors.affiliation: Laboratory of Molecular Endocrinology, School of Fisheries Sciences, Kitasato University, Iwate, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Noso
authors.forename: C S
authors.initials: CS
authors.lastname: Nicoll
authors.forename: H
authors.initials: H
authors.lastname: Kawauchi
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D005075:Biological Evolution; D005399:Fishes / Q000378:metabolism*; D008969:Molecular Sequence Data; D010902:Pituitary Gland / Q000201:enzymology*; D011388:Prolactin / Q000737:chemistry* / Q000235:genetics; D013045:Species Specificity
chemical_list: D000596:Amino Acids; D011388:Prolactin