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The Low Polarity of Many Membrane Proteins

Roderick A. Capaldi and Garret Vanderkooi
Proceedings of the National Academy of Sciences of the United States of America
Vol. 69, No. 4 (Apr., 1972), pp. 930-932
Stable URL: http://www.jstor.org/stable/61736
Page Count: 3
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
The Low Polarity of Many Membrane Proteins
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Abstract

The polarities of a large number of soluble and membrane proteins have been calculated by summing the mole fractions of polar amino acids. It was found that 85% of the 205 soluble proteins considered in this study had polarities of 47 ± 6%. Only 2% of the soluble proteins had polarities below 40%, whereas 47% of the 19 membrane proteins had polarities below 40%. The membrane proteins with polarities below 40% could be separated from their respective membranes only by detergents or organic solvents, indicating the importance of hydrophobic forces in their interaction with other membrane components. It is concluded that the majority of ``intrinsic'' membrane proteins have low polarity, and that the polarity index is therefore a useful parameter for characterization of membrane proteins.

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