Hydropathic index

To verify functional results using synthetic peptides, antipeptide antisera were produced [14]. All antipeptide antisera were reactive with the native molecule. Interestingly, antisera titers correlated with the hydropathic index of the peptide, rather than with the predicted surface accessibility of the specific region in the 3-D configuration. Consistent with the peptide studies, antisera against the same four regions of the molecule inhibited IFN- activity while antisera to other regions did not. 

Membrane-bound proteins extend from the cytoplasmic membrane. Analysis by the method of Kyte and Doolittle 186> is quite useful for predicting the protein segments extending into the cytoplasmic membrane. The Kyte and Doolittle method, the so-called hydropathic index method, if it is coupled with the Chou-Fasman method, safely differentiates the protein segment which is located outside the membrane, from the helices within the membrane. The best examples are cytochrome P-450 187), cytochrome b5188), reaction centers 189,190) and light-harvesting protein comple-... 

Hydropathy plot. The hydropathic index is plotted on they axis, with hydrophobic domains at the top and hydrophilic domains at the bottom. The x axis shows the amino-acid residue number from the amino to the carboxy terminus. The protein shown is a 7-transmembrane receptor (the serotonin receptor), analogous to the epinephrine (adrenalin) receptor. The approximate positions of the seven transmembrane segments are indicated by the purple bars. (Original plot graciously provided by... 

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