Variant polypeptides

Haidaris, P. J., Francis, G. W., Sporn, L. A., Arvan, D. S., Collichio, F. A., and Marder, V. J. (1989). Megakaryocyte and hepatocyte origins of human fibrinogen biosynthesis exhibit hepatocyte-specific expression of gamma chain-variant polypeptides. Blood 74, 743-750. 

Polymorphic variant A gene, mRNA, cDNA, polypeptide or peptide whose nucleotide or amino acid sequence varies from a reference sequence due to the presence of a polymorphism in the gene. 

G-CSF is also known as pluripoietin and CSI -fl. Two slight variants are known, one consisting of 174 amino acids and the other of 177. The smaller polypeptide predominates and also displays significantly greater biological activity than the larger variant. 

When chromatographic resolution of species based on modifications located at the protein surface is desired, it may be advisable to use conditions that favor retention of native conformation.17 Here, the standard acidic conditions described in the preceding text may be inappropriate, and mobile phases buffered near neutrality may be required. Buffers based on ammonium acetate, ammonium bicarbonate, and triethylammonium phosphate may prove more useful in resolving polypeptide variants with differing posttranslational modifications, amino acid substitutions, or oxidation and deamidation products. The addition of more hydro-phobic ion-pairing agents may be needed to obtain polypeptide retention, and a variety of alkyl sulfonates and alkyl amines have been described for specific applications.17... 

Biopharmaceuticals based on natural proteins and peptides are often called by the same name as the biologic natural material despite differences in one or more amino-acid residues. For example, insulin, which regulates blood glucose and is used clinically to treat type 1 diabetes and some cases of type 2 diabetes, has several variants that are approved for human use. Insulin contains two polypeptides, A and B chains (Figure 1.2), that are linked together by two disulfide bridges to assume a biologically active conformation. Compared with human insulin, insulin extracted from beef tissue exhibits threonine alanine and isoleucine valine substitutions at posi-... 

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