Glycosylated human growth hormone (hGH): a novel 24 kDa hGH-N variant

We have identified a human pituitary protein as a novel glycosylated variant of hGH. Isolation of the denatured protein included separation of human pituitary extract by Sephadex G-100 chromatography in ammonium bicarbonate, followed by Sephadex G-100 chromatography in 10% acetic acid, with subsequent DEAE Sephacryl chromatography in ammonium bicarbonate, and finally by preparative SDS PAGE. The pituitary protein has a molecular weight of 24 kDa as determined by SDS PAGE analysis and is thus larger than the normal 22 kDa hGH. N-Terminal amino acid sequence analysis of the first twenty-six residues reveals that this protein is not derived from the hGH-V gene but is rather a hGH-N gene product. Assays for the detection of glycoconjugates (periodate oxidation, sialidase treatment, trifluoromethanesulfonic acid treatment) indicate that the hGH variant has carbohydrate moieties. The discovery of new hGH raises questions about the role of glycosylation in the structure/function relationships of this hormone.