a possible role for metallic ions in the carbohydrate cluster recognition displayed by a lewis y specific antibody碳水化合物集群中的可能作用的金属离子识别显示由刘易斯y特异性抗体.pdfVIP

A Possible Role for Metallic Ions in the Carbohydrate Cluster Recognition Displayed by a Lewis Y Specific Antibody 1 2 1,3,4 William Farrugia , Andrew M. Scott , Paul A. Ramsland * 1 Centre for Immunology, Burnet Institute, Melbourne, Victoria, Australia, 2 Tumour Targeting Program, Ludwig Institute for Cancer Research, Austin Health, Heidelberg, Victoria, Australia, 3 Department of Surgery (Austin Health/Northern Heath), The University of Melbourne, Heidelberg, Victoria, Australia, 4 Department of Immunology, Monash University, Alfred Medical Research and Education Precinct, Melbourne, Victoria, Australia Abstract y Background: Lewis Y (Le ) is a blood group-related carbohydrate that is expressed at high surface densities on the majority of epithelial carcinomas and is a promising target for antibody-based immunotherapy. A humanized Ley-specific antibody (hu3S193) has shown encouraging safety, pharmacokinetic and tumor-targeting properties in recently completed Phase I clinical trials. Methodology/Principal Findings: We report the three-dimensional structures for both the free (unliganded) and bound (Ley tetrasaccharide) hu3S193 Fab from the same crystal grown in the presence of divalent zinc ions. There is no evidence of significant conformational changes occurring in either the Ley carbohydrate antigen or the hu3S193 binding site, which suggests a rigid fit binding mechanism. In the crystal, the hu3S193 Fab molecules are coordinated at their protein-protein interface by two zinc ions and in solution aggregation of Fab can be initiated by zinc, but not magnesium ions. Dynamic light scattering revealed that zinc ions could initiate a sharp transition from hu3S193 Fab monomers to large multimeric aggregates in