Purification and characterization of a fetal XXXX from the sheep: similarity to insulin-like growth factor II.

@entity1 @entity1472 @entity535 @entity5100 @entity9418 @entity35 @entity291
A high efficiency procedure for the purification to homogeneity of an ovine fetal @entity9418 is described. Fetal sheep serum was used as the source material, and activity was followed throughout purification by an @entity5100 RRA. @entity5100 -like activity was initially enriched through binding at acid pH to a column of SP-Sephadex C-25 and elution with a neutral pH high-salt buffer. Further chromatography on SP-Sephadex resulted in a preparation containing less than 0.1% of the original serum protein content, but retaining much of the @entity5100 -like activity. This enriched fetal IGF preparation was then purified to homogeneity using reverse phase HPLC. However, chromatography on an HPLC gel filtration column was found to be essential to ensure the stability of the purified peptide during storage, although this procedure did not result in any apparent increase in purification. The final yield of purified ovine fetal IGF was 80 micrograms from 400 ml fetal sheep serum. Only one polypeptide chain was detected during @entity1472 -terminal sequencing of the fetal @entity9418 , and the preparation gave a single band on both gel electrophoresis and isoelectric focusing, indicating that the peptide was essentially pure. The sequence (eight @entity535 residues) was identical to the equivalent sequence in @entity5100 from @entity1 , @entity35 , and @entity291 sources. In additional, @entity535 analysis of the ovine fetal IGF showed close similarity to the @entity535 content of @entity5100 from other species. The mol wt of the purified peptide, estimated by HPLC gel filtration, was approximately 7000, close to that of previously purified somatomedins, and the isoelectric point, obtained by chromatofocusing, was around pH 6.8. Thus, the purified ovine fetal @entity9418 appears to be similar to @entity5100 from other species, and may be the ovine homolog of @entity1 @entity5100 .
