Biophysical studies on two conformations of a human plasma lipoprotein

Autor: Charles R. Harmison
Rok vydání: 2009
Předmět:
Zdroj: International Journal of Quantum Chemistry. 9:117-128
ISSN: 1097-461X
0020-7608
DOI: 10.1002/qua.560090710
Popis: Two forms of an alpha-2-globulin (a lipoprotein) have been isolated from individual human plasmas. They are the same in amino acid and lipid compositions, but they differ in trans-membrane transport activities and in their in vivo activities. The form from control subjects, which is nonhelical in conformation, seems to be devoid of biological activities. The other form is from patients with schizophrenia, has variable ff, and promotes trans-membrane transport of tryptophan. From biophysical measurements on pooled samples, the apparent S20.w = 0.46 and 0.44 for the patients' sample and the control sample, respectively. The apparent D20, w = 1.25 and 1.22, respectively, for the two forms. With v = 0.968, the molecular weights from the Svedberg equation were found to be 263,500 ± 2,500. With a 20% protein content, the protein moiety is close to 53,000 Daltons, which is much less than that for many other lipoproteins. With [η] = 0.0264, the helical conformation is globular in shape and nearly spherical. For the nonhelical conformation, [η] = 0.0369, which signifies an increased molecular asymmetry. In amino acid composition this alpha-2-globulin is different from the β lipoprotein (LDL) and from the HDL-1, but it is quite similar to that of the HDL2.
Databáze: OpenAIRE
Externí odkaz: