High-level expression of recombinant human growth hormone (hGH) in Escherichia coli (E. coli) leads to the formation of\r\ninsoluble aggregates as inclusion bodies devoid of biological activity. Until recently, significant efforts have been made to\r\nimprove the recovery of active hGH from inclusion bodies. Here, we developed an efficient procedure for the production of\r\ncompletely soluble hGH by minimizing the formation of inclusion bodies and optimizing protein purification conditions.\r\nUnder the newly established conditions we were able to obtain most of the total hGH in the soluble fraction. We show that\r\nthe soluble protein can be efficiently purified in high yield by a series of chromatographic procedures. We analyzed the\r\nresulting hGH using various analytical techniques such as reversed-phase high-performance liquid chromatography (RPHPLC),\r\nsize-exclusion chromatography (SEC), matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass\r\nspectrometry, and circular dichroism (CD). These multiple analyses support the conclusion that we obtained highly pure\r\nhGH with the expected molecular mass and intact secondary structure. The biological activity of purified hGH was also\r\nconfirmed by evaluating its growth-promoting effect using a cell proliferation assay. Taken together, we describe a\r\nstraightforward strategy for the production of completely soluble and biologically active hGH in E. coli.
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