Neurophysin fractionation

They also reported that neurophysin fraction E bound two Moles of 8-lysine vasopressin per Mole of protein agreeing with the results obtained by us with neurophysin-II but not for neurophysin-I or M which both bind three Moles of the polypeptide. The results of Breslow and Abrash 52 revealed the presence of only two peptide binding sites in their protein fraction whereas those reported here show that there are three in neurophysin-I,... 

In this and other respects e.g histidine was absent, it was different from the so-called van Dyke protein. We decided to call the major sub-fraction neurophysin-M until more was known about it and a better name could be found. Neurophysin-M behaved as a homogeneous protein in the ultracentrifuge and assuming a partial specific volume of 0.7 9 ml. per g. a molecular weight of 23 000 was calculated. During the course of the work we began to study the electrophoretic behaviour of the proteins in the buffer devised by Ferguson and Wallace In this system neurophysin-M... 

As already discussed neurophysin-M consisted of two protein components separable by electrophoresis. One of the two constituents occurred in neurosecretory granules and the other appeared to be a degradation product. When attempts were made to separate them by fractional precipitation in the presence of vasopressin by the addition of increasing amounts of salt the proportion of the two remained constant. However, after a few days the amorphous precipitate kept at crystallized. This was interesting because it was the first time that vasopressin had been obtained in crystalline form 26, The need to separate the two proteins in neurophysin-M was removed when it was found that only one of them was present in extracts of an acetone powder of pituitary tissue. 

The binding of two Moles of oxytocin by neurophysin-II and neurophysin-M is in agreement with the finding of Breslow and Abrash for a fraction (E) of bovine neurophysin. The native neurophysin-I has been found to bind three Moles of oxytocin per Mole of protein. Neurophysin-I would have been absent from the preparations of neurophysin used by Breslow and Abrash 52 ... 

In making studies of the possible participation of neurophysin in the mechanism of release, it should be recalled, that recent studies have indicated that the chemical properties of neurophysin may vary with the preparation technique (Dean et al. 1967). It seems that special precautions should be taken when isolating neurophysin, to obtain a product similar to the natural one. It may bevhowever, that studies of binding properties of neurophysin obtained by previous techniques have still yielded reasonable information, since nearly all of the fractions, produced by different preparation procedures, do bind hormones. There has been... 

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