Practice question

Early industrial production human insulin 1982 relied fusion protein technology because small 51 aa insulin A 21 B 30 rapidly degraded bacterial cytoplasm proteases Lon Clp if expressed mature alone. Genentech team Riggs Boyer Goeddel chemically synthesized DNA encoding insulin chains separately fused carboxy terminus E. coli beta-galactosidase 1024 aa enzyme encoded lacZ or trp leader peptide. Large fusion drove formation insoluble inclusion bodies protecting heterologous peptide from proteolysis enabling purification centrifugation detergent washes. Construct single methionine codon junction providing CNBr cleavage site. After solubilization formic acid cleavage S-sulfonated A B chains purified gel filtration ion exchange mixed equimolar ratio oxidative conditions reduced oxidized glutathione facilitating correct disulfide bonds A6-A11 intrachain A7-B7 A20-B19 interchain yielding biologically active insulin identical human pancreatic hormone lacking immunogenic contaminants bovine insulin. Product entered market Humulin first recombinant pharmaceutical approved FDA October 1982, pioneering biotech industry demonstrating recombinant protein production commercial viability subsequently adapted for growth hormone.