Synthesis of a new helical protein: the effect of secondary structure rearrangement on structure formation

A new helical protein was designed and synthesized to alter the sequential connectivity of the 4 helices in human growth hormone and to delete the long surface loop structures. The protein accumulated as an insoluble form in E. coli was solubilized and purified to apparent homogeneity in the presence of 7M urea, and refolded by the aid of 1% n-octyl-beta-D-glucopyranoside. The circular dichroism spectrum was typical of a highly helical protein. The molecular weight estimated by gel permeation chromatography and the red-shift of the fluorescence maximum by urea-induced denaturation suggest that the protein folds into a compact globular form. The new protein obtained, however, was destabilized relative to the original human growth hormone.