出版社：American Society for Biochemistry and Molecular Biology
摘要：Previous studies demonstrated that structural perturbation of the α1 domain of apolipoprotein B (apoB) blocked the initiation of lipoprotein assembly. We explored the hypothesis that this domain may interact with the inner leaflet of the endoplasmic reticulum membrane in a manner that may nucleate microsomal triglyceride transfer protein-dependent lipid sequestration. ApoB-17 (amino-terminal 17% of apoB), which contains most of the α1 domain, was expressed stably in rat hepatoma cells and recovered from medium in lipid-poor form. On incubation with phospholipid vesicles composed of 1-myristol-2-myristoyl- sn -glycero-3-phosphocholine or 1-palmitoyl-2-oleoyl- sn -gylycero-3-phosphocholine, apoB-17 underwent vesicle binding and was recovered in the d 1 domain of apoB are stabilized by intramolecular disulfide bonds. In contrast to apoB-17 chemically reduced in vitro, forms of apoB-17 bearing pairwise cysteine-to-serine substitutions were recovered in soluble form from transiently transfected COS-1 cell extracts. Although individual disruption of disulfide bond 2 or 4 in apoB-28 and apoB-50 was previously shown to block lipoprotein assembly in vivo, these alterations had no impact on the ability of apoB-17 to bind to phospholipid vesicles in vitro or on its capacity to form recombinant lipoprotein particles. These results suggest that while the vesicle/lipid-binding property of the α1 domain may reflect an essential role required for the initiation of lipoprotein formation, some other aspect of α1 domain function is perturbed by disruption of native disulfide bonds. —DeLozier, J. A., J. S. Parks, and G. S. Shelness. Vesicle-binding properties of wild-type and cysteine mutant forms of α1 domain of apolipoprotein B. J. Lipid Res. 2001. 42: 399–406.
