SECRETORY EXPRESSION OF HUMAN ALBUMIN DOMAINS IN SACCHAROMYCES-CEREVISIAE AND THEIR BINDING OF MYRISTIC ACID AND AN ACYLATED INSULIN ANALOG

Albumin is organized in three homologous domains formed by double loop s stabilized by disulfide bonds. Utilizing a secretory expression syst em based on a synthetic secretory prepro-leader, the three human serum albumin domains were expressed in the yeast Saccharomyces cerevisiae. Human serum albumin domains I and III were efficiently expressed and secreted, indicating that these domains can form independent structura l units capable of folding into stable tertiary structures. In contras t, albumin domain II was not secreted and disappeared early in the sec retory pathway. Human serum albumin has the ability to bind a large nu mber of small molecule ligands, including fatty acids, presumably due to its structure and structural flexibility. Purified albumin domain I II bound myristic acid, whereas purified albumin domain I did not bind myristic acid. A new soluble long-acting insulin an alogue acylated w ith myristic acid (Markussen J., et al., Diabetologia 39, 281-288, 199 6) bound to domain III and bound markedly more weakly to domain I. (C) 1998 Academic Press.