The isolation of three neurophysins from porcine posterior pituitary lobes.
1. Three neurophysins, proteins that bind the polypeptide hormones oxytocin and vasopressin, have been isolated from acetone-dried porcine posterior pituitary lobes. The proteins have been named porcine neurophysins-I, -II and -III in order of their electrophoretic mobilities at pH8.1. 2. Electrophoretic comparison of the purified proteins, which are homogeneous on starch-gel electrophoresis, with the soluble proteins of fresh porcine posterior pituitary lobes extracted in 0.1m-HCl and in buffer pH8.1 suggests that the isolated proteins are native to the fresh tissue. 3. Neurophysins-I and -II are present in similar amounts in the tissue, whereas neurophysin-III is present only in small quantities. Acetone-dried tissue also contains traces of other hormone-binding neurophysin components. 4. All the neurophysins can bind both oxytocin and [8-lysine]-vasopressin. 5. The apparent molecular weights of the neurophysins increase with increasing protein concentration as measured by equilibrium sedimentation in the ultracentrifuge. 6. Neurophysins-I and -III are of similar molecular dimensions, contain one residue of methionine per molecule and lack histidine. The minimum molecular weight of neurophysin-I obtained by amino acid analysis is 9360. Neurophysin-II is of larger molecular dimensions than neurophysins-I and -III and can be separated from these by gel filtration on Sephadex G-75. It contains no histidine or methionine, and its minimum molecular weight has been estimated as 14020 by amino acid analysis. 7. Each of the three neurophysins possesses N-terminal alanine. 8. The possible biological significance of the existence of several neurophysins within one species is discussed.
D000409:Alanine / Q000032:analysis; D000818:Animals; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D004586:Electrophoresis; D006863:Hydrogen-Ion Concentration; D008715:Methionine / Q000032:analysis; D008970:Molecular Weight; D010904:Pituitary Gland, Posterior / Q000032:analysis*; D010909:Pituitary Hormones, Posterior / Q000302:isolation & purification*; D011485:Protein Binding; D011506:Proteins / Q000302:isolation & purification*; D013552:Swine; D014461:Ultracentrifugation
D010909:Pituitary Hormones, Posterior; D011506:Proteins; D008715:Methionine; D000409:Alanine