Vascular endothelial growth factor (VEGF) has been found to have various functions on endothelial cells, the most prominent of which is the induction of proliferation and differentiation. In this report we demonstrate that VEGF or a mutant, selectively binding to the Flk-1/ KDR receptor, displayed high levels of survival activity, whereas Flt-1-specific ligands failed to promote survival of serum-starved primary human endothelial cells.
The deduced amino acid sequence of human factor VIII, obtained from the DNA sequence, predicts a mature polypeptide of 2,332 amino acids containing a triplicated domain structure. The polypeptide has 35% sequence homology with the copper-binding plasma protein, ceruloplasmin. Determination of the thrombin cleavage sites in plasma-derived factor VIII polypeptides allows prediction of the domains involved in the associated activation and inactivation of the protein.
DNA clones encoding the complete 2,351 amino acid sequence for human factor VIII have been isolated and used to produce biologically active factor VIII in cultured mammalian cells. The recombinant protein corrects the clotting time of plasma from haemophiliacs and has many of the biochemical and immunological characteristics of serum-derived factor VIII.
A comparison of the eight independent copies of VEGF in the asymmetric unit indicates the conformational space sampled by the protein in solution; the root mean square differences observed are similar to those seen in ensembles of the highest precision NMR structures. Mapping the receptor-binding determinants on a multiple sequence alignment of VEGF homologs, suggests the differences in specificity towards KDR and Flt-1 may derive from both sequence variation and changes in the flexibility of binding loops. The structure can also be used to predict possible receptor-binding determinants for related cystine knot growth factors, such as PDGF.
The heparin-binding domain of VEGF has no significant sequence or structural similarity to any known proteins and thus represents a novel heparin-binding domain. Most of the positively charged amino acid sidechains are localized on one side of the carboxy-terminal subdomain or on an adjacent disordered loop in the amino-terminal subdomain. The observed distribution of surface charges suggests that these residues constitute a heparin interaction site.
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