Research from Royal North Shore Hospital has provided new data on apoptosis
2007 NOV 21 -- "Mass spectrometry is often used to determine post-translational modifications by analysis of tryptic digests of proteins. Here we demonstrate that the analysis of tryptic peptides together with analysis of the full-length protein provided optimal characterization of insulin-like growth factor-binding protein-5 (IGFBP-5) phosphorylation and glycosylation," scientists in Australia report. "IGFBP-5 binds insulin-like growth factors with high affinity and has important roles in cell survival, differentiation, and apoptosis. Until now, the primary structure of IGFBP-5 has been incompletely defined. We analyzed human IGFBP-5 from T47D cells by mass spectrometry to determine all of the in vivo post-translational modifications. In full-length IGFBP-5, 31% of the protein was unmodified, 37% was monophosphorylated, and 4% was diphosphorylated with no other modification. The remaining 27% was glycosylated, more than half of which was also monophosphorylated. The major phosphorylation site was Ser(96) in the central domain, and a minor phosphorylation site was Ser(248) near the C terminus. Neither site was phosphorylated in vitro by casein kinase 2, ruling it out as the in vivo kinase. An in vivo phosphorylation site was also found in IGFBP-2 at an analogous position, Ser(106). IGFBP-5 was heterogeneously O-glycosylated mainly by sialylated core 1 type glycans. The most abundant structure contained N-acetylhexosamine, hexose, and two N-acetylneuraminic acid carbohydrates. A small amount of sialylated core 2 type glycan was also present. Phosphorylation and O-glycosylation both affected IGFBP-5 binding to heparin but not insulin-like growth factor binding or ternary complex formation with the acid-labile subunit," wrote M.E. Graham and colleagues, Royal North Shore Hospital. The researchers concluded: "The results reveal the first description of the in vivo phosphorylation of IGFBP-5 and its glycan composition." Graham and colleagues published their study in Molecular & Cellular Proteomics (The in vivo phosphorylation and glycosylation of human insulin-like growth factor-binding protein-5. Molecular & Cellular Proteomics, 2007;6(8):1392-1405). For more information, contact R.C. Baxter, Royal North Shore Hospital, Kolling Institute Med Research, St. Leonards, NSW 2065, Australia. Publisher contact information for the journal Molecular & Cellular Proteomics is: American Society Biochemistry Molecular Biology Inc., 9650 Rockville Pike, Bethesda, MD 20814-3996, USA. Keywords: Australia, Apoptosis, Royal North Shore Hospital. This article was prepared by Biotech Week editors from staff and other reports. Copyright 2007, Biotech Week via NewsRx.com.
|
