Some examples of labeling with hydrophobic reagents

Some examples of labeling with hydrophobic reagents 

In this section the case of glycophorin, which has proved to be straightforward, and the case of Na,K-ATPase, in which some complications have arisen, are briefly discussed. 

Both [5-12SI]iodonaphthylazide (Karlish et al. 1977) and [3H]adaman-tane diazirine (Farley et al. 1980) labeled the a-subunit strongly and the (3-subunit hardly at all. The simplest interpretation of this result is that the (3-subunit is a peripheral protein, tightly attached to the a-subunit. The possibility remains, however, that the (3-subunit is relatively unreactive towards hydrophobic reagents even though the two used in these studies have quite different properties. A further possibility that must be taken into account when considering multisubunit membrane proteins is that (3 penetrates the bi layer but is shielded from the hydrocarbon phase by neighboring a-subunits.  

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