Structural and functional characterisation of recombinant human erythropoietin analogues.

Deletion mutants of a synthetic human erythropoietin-cDNA were transiently expressed in COS-7 cells and products analyzed using Western blots and a cell proliferation assay. Only two mutants with deletions affecting the N-terminal portion and the amino acid sequence 115-121 displayed biological activity. The exchange of hydrophilic, charged amino acids by alanine in two potential alpha-helical regions, the internal amino acid sequence 102-106 and the C-terminal sequence 154-159, causes a 2-11-fold loss of activity. The results suggest that both regions are involved in either maintaining the active structure of the hormone or interacting with the receptor.