Protein Structural Isoforms

Protein synthesis is accompanied by some important events, termed post-translational modifications, that convert the information carried by a two-dimensional polypeptide into a complex, biologically active three-dimensional protein. These modifications encompass events such as protein folding and phosphorylation, glycosylation, sulfation and myristoylation. Variations in post-translational modifications lead to variants of a protein that are products of the same gene but may vary in structure, function, pharmacokinetics and pharmacodynamics. Glycosylation, the most important event during protein synthesis, has received much attention in the last few years due to its influence on the clinical and therapeutic properties of proteins. Most biopharmaceuticals produced by recombinant DNA technology, such as erythroprotein and tissue-plasminogen activator for in vivo administration, are glycosylated. These may suffer from glycoform heterogeneity due to variations in the carbohydrate sequence or due to variable site occupancy of the sugar moieties on the protein. Consequently, it is important to isolate, resolve and analyse recombinant glycoforms with defined glycosylation and biological properties prior to clinical prescription.

The strategy for the resolution of glycoforms involves generation of synthetic ligands that display affinity and selectivity for the sugar moieties on glycoproteins but have no interaction with the protein per se. A detailed assessment of native protein-carbohydrate interactions using molecular modelling tools formed the basis for the synthesis of carbohydrate-binding ligands. The ligands were synthesized on a solid phase and assessed for their sugar-binding ability with glycoenzymes. Chromatography

Figure 4 (See Colour Plate 18) Molecular model between the Fc fragment of IgG and the synthetic ligand ApA. The ligand, in red, is a mimic ofthe key dipeptide Phe-Tyr, in green, in SpAand comprises anilino andtyramino moieties substituted on a triazinyl framework. ApA is located at the putative binding site among the amino acid residues involved in the interaction between the Fc part of IgG and Fb fragment of SpA.

Figure 4 (See Colour Plate 18) Molecular model between the Fc fragment of IgG and the synthetic ligand ApA. The ligand, in red, is a mimic ofthe key dipeptide Phe-Tyr, in green, in SpAand comprises anilino andtyramino moieties substituted on a triazinyl framework. ApA is located at the putative binding site among the amino acid residues involved in the interaction between the Fc part of IgG and Fb fragment of SpA.

with partially and completely deglycosylated enzymes, elution of glycoproteins with sugars and inhibition of glycoproteins for the synthetic receptor in the presence of free sugars helped to assess the selectivity of the ligands for the sugars. Palanisamy and co-workers (1999) observed that triazine-based ligands display selectivity for the glycomoieties on glycopro-teins and identified mannose-binding synthetic ligands.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

Get My Free Ebook


Post a comment