Analysis of computer-generated hydropathy profiles for human glycoprotein and lactogenic hormones

Analysis of hydrophobic and hydrophilic regions of human lactogenic (PRL, GH, and placental lactogen) and glycoprotein hormones (FSH, LH, TSH, and hCG) by the method of Kyte and Doolittle has been performed. A BASIC program, developed for the IBM personal computer, produces graphical and tabular results. The net hydropathy value, a new parameter based on the Kyte and Doolittle analysis which may be useful for comparing various polypeptides, was developed. This value is correlated with physical properties, such as solubility of the glycoprotein hormones. New (more hydrophilic) indices were assigned for glycosylated asparagine, serine, and threonine residues, and slightly more hydrophilic indices were assigned for half-cystines found in disulfide bonds. The results indicate that the so-called determinant loop of Ward and Moore is hydrophilic (accessible) and suggest that regions on either side of this loop should also be considered as potential effectors of hormone specificity. It is suggested that binding (protein-protein interaction) sites tend to be modestly hydrophilic, but also contain residues that could interact through the hydrophobic effect.