Loss of liposome binding of NADH dehydrogenase from alkalophilic Bacillus on subtilisin digestion

Alkalophile NADH dehydrogenase consisting of two 65‐kDa subunits was changed by subtilisin into an enzyme species consisting of two 38‐kDa subunits. The amino acid composition and enzyme activity per molecule of the subtilisin‐treated enzyme were almost the same as those of the native enzyme, respectively. On mixing with phospholipid liposome, the conformation of the native enzyme was changed, as suggested by the changes in the type ofArrhenius plot and of CD spectrum and enzyme activity. These conformational properties of the subtilisin‐treated enzyme, on the other hand, were not affected by liposome. Gel filtration of the subtilisin‐treated enzyme mixed with the liposome showed no binding of the protein to liposome.