The molecular weights of porcine plasma high density lipoprotein and its subunits.

The molecular weights of the dcnsclr fraction of porcine plasma high density (1.1 lo 1.2 g per ml) lipoprotein and its protein subunits were estimated to determine the number of chains and to characterize the molecular species for further studies. These estimates are compared with those reported for human HDL3.’ Shore and Shore (1) deduced that human plasma HDL, was compoerd of three identical protein subunits, each with a molccular weight of 37,000, and lipid complrmcnt. This deduction was based upon their estimates of tho molecular weights by approach to sedimentation equilibrium, by determinat.ion of lipid composition, and by quantitative determination of NH,terminal amino acids. More reccnt.ly, they have revised their estimate of the subunit’s molecular weights from 37,000 lo 32,000 as the result of more precise measurements (2, 3). Sranu (4) determined the molecular weight.?; of all of the protein subunits for human plasma IIDL, HDL,, and IIDL, to hnve an average value of 21,000, and hr concluded that IIDLI contains an average of five subunits, while IlDL? contains an average of seven. Subsequently, Scanu (5) reported the subunit’s molecular weights to be 24,000 f 2,000; more recent.ly, Scanu, Reader, and Edelstein (6) reported 25,800 f 1,000. Shore and Shore (2) reported that HDLz contains a different protein, with a molecular weight of 23,000, and has a different amino acid composition.