Synergy and collaboration: keys strategies of Walk-it Bunbury

The present invention relates to isolated sialyltransferases, such as human or mouse GM3 synthase, human or mouse 4ST3GalVI, or human 7STGalNAcV sialyltransferase polypeptide, biologically-active polypeptide fragments thereof, and nucleic acids which code for it. This polypeptide has various activities including sialyltransferase activity. The invention relates to all aspects of sialyltransferase, or homologs thereof, including assays for modulators, activators, ligands, etc. The invention also relates to sialyltransferases expressed in cells and methods of using such cells to engineer specific sugar chains.