Title :
Peptide , disulfide, and glycosylation mapping of recombinant human
thrombopoietin from
ser1 to
Arg246
Abstract :
- Thrombopoietin ( TPO ) is a hematopoietic factor involved in the regulation of megakaryocytopoiesis
- Full length recombinant human TPO (332 residues ) has been expressed in BHK cells and purified to homogeneity using conventional means
- Peptide , disulfide, and glycosylation mapping of human TPO from residues 1 to 246 has been carried out using liquid chromatography-electrospray mass spectrometry (LC-ESMS)
- A modification of the ramped orifice method of Carr and co-workers [ Carr et al. ( 1993 ) Protein Sci
- 2, 183-196] is employed, providing additional information for assignment of the LC-ESMS chromatograms
- With the modification, b- and y-series peptide ions are produced via front-end CID which confirms the mass-based assignments
- The results of our analysis of TPO indicate that the amino acid sequence of TPO 1-246 is as expected from the transfected cDNA with complete cleavage of the signal peptide
- Two unique disulfides are formed between the four cysteines in the cytokine domain of TPO : Cys7-Cys151 and Cys29-Cys85
- The glycosylation map indicates the position, occupancy, and structures of the N- and O-glycans in TPO 1-246
- In addition, site specific structural characterization of the PNGase F-liberated N-glycans has been performed following purification by high-pH anionic exchange chromatography with pulsed amperometric detection (HPAEC-PAD); the results corroborate the LC-ESMS data
- The N-glycans are of the complex type with the core-fucosylated disialylated biantennary and trisialylated triantennary structures predominating
- The O-glycans are of the mucin type with the monosialylated and disialylated GalGalNAc-S/T structures predominating
- Furthermore, we propose that the C-terminal domain of TPO be further divided into two domains on the basis of sequence homology among the cloned sequences and glycosylation/structural features: an N-glycan domain (154-246) and an O-glycan domain (247-332)