The antiangiogenic and antitumor activities of the N-terminal fragment of endostatin augmented by Ile/Arg substitution: The overall structure implicated the biological activity.

The antiangiogenic and antitumor activities of the 27-amino acid fragment corresponding to the N-terminal domain of endostatin were shown to be dependent on a Zn-binding loop in the N-terminus. To investigate whether the regions outside of the N-terminal loop play a role in the peptide function, the structure and function of a variant containing Ile26Arg mutation (ES-R) were compared with those of the native peptide (ES-Zn). Structural analysis using far-UV CD, intrinsic fluorescence and molecular dynamics simulation provided information regarding the overall changes upon the mutation. In addition, the docking simulations predicted a higher affinity of ES-R to integrins αβ and αβ than ES-Zn and a profound reorganization of the binding residues throughout the sequence. In Human Umbilical Vein Endothelial Cells (HUVECs), ES-R inhibited the tube formation and activated caspase-3 more strongly than do ES-Zn. Based on in vivo studies, the growth of breast tumor and expression of CD31, Bcl-2 and nonfunctional p53 were inhibited more effectively by ES-R than by ES-Zn. We conclude that the C-terminal region is involved in the peptide function through some global structural effects.