Fig. 4.

Purification of OMM-associated SR from rat heart mitochondria. Submitochondrial fractions (20–24) were separated on a sucrose density gradient. The approximate mapping of the fractions to the sucrose density levels is illustrated by the scheme at left. A: bimodal protein profile is shown at the bottom; enzyme activities of HK (○; OMM marker), MAO (●; OMM marker), and SDH (squares; IMM marker) in the subfractions (normalized to maximum) are shown at top. Data are means ± SE from 3 preparations (HK, SDH) or means ± range from 2 preparations (MAO). B: representative Western blots of CIII (IMM marker) and SERCA2a from the submitochondrial fractions shown in A.