Henry Acken Havel

Effects of surface hydrophobicity on the structural properties of insulin

Publisher Summary This chapter discusses the effects of increasing the surface hydrophobicity of a globular protein. It has chosen to address this by comparing the conformational stability of a model protein in the presence and absence of a hydrophobic group attached covalently to a specific surface residue. Human insulin (HI) has been selected as the model protein because of its relatively small polypeptide for which there is a wealth of structural, chemical, and biological information. In addition, the insulin molecule possesses a rich conformational chemistry distinguished by thoroughly characterized structural transitions and ligand binding processes. The derivative bearing a surface hydrophobic group that is the subject of this study is N ɛ -palmitoylLys B29 human insulin (Pal-HI). In this chapter, Lys B29 has been chosen as the acylation site because of the simplicity of its conjugation chemistry. This residue resides in the C-terminus of the B-chain, which is a region of the insulin molecule known to be extremely flexible, and this region probably plays a minor role in the folding and unfolding process of unmodified insulin.

MOLECULAR CHARACTERIZATION OF AN AGGREGATE FORMED BY A BOVINE GROWTH HORMONE FOLDING INTERMEDIATE

Publisher Summary Bovine growth hormone (bGH) aggregates following partial denaturation at elevated concentrations. Human growth hormone (hGH), on the other hand, does not aggregate under these conditions. The difference in the folding behavior of these homologous proteins may account for the observation that hGH does not necessarily form inclusion bodies. Folding studies of bGH indicate that the formation of the bGH folding intermediate and its aggregation are separate processes, implying that selective protein modifications may lead to their independent modulation. This chapter presents the results of solubility and spectral experiments involving R108N and E126R. The solubility studies suggest that both analogs aggregate to the same extent as wild-type bGH. Experiments were undertaken to identify structural elements of bGH that help stabilize the aggregation of partially denatured protein. The data presented from solubility experiments show that R108N and E126R, two of the amino acid substitutions included within 8H-bGH, do not appear to appreciably destabilize the formation of the partially denatured, aggregated species.