Systematic expression of the complete coding sequence of apoB-100 does not reveal transmembrane determinants.

Leiper, J.M. , Harrison, G.B., Bayliss, J., Scott, J.D. and Pease, R.J. (1996) Systematic expression of the complete coding sequence of apoB-100 does not reveal transmembrane determinants. Journal of Lipid Research, 37(10), pp. 2215-2231. (PMID:8906598)

Full text not currently available from Enlighten.

Abstract

We have investigated the hypothesis that apolipoprotein B undergoes a regulated process of translocation into the endoplasmic reticulum (ER) which causes the protein to adopt a transmembrane configuration. Protein segments representing the complete coding sequence of apolipoprotein B were first expressed by in vitro translation of transcripts from seven overlapping transcripts. Two regions were identified (located at residue 2425 and between residues 4149 and 4348) that can undergo incomplete translocation into pancreatic microsomes. Ribosome pausing at these sites uncoupled translation from translocation, leading to the synthesis of large cytoplasmically oriented segments of protein. In contrast, when these two regions were expressed by transfection in cultured cells, transmembrane structures were not detected. Endogenous apolipoprotein B-100 synthesis in HepG2 cells generates a spectrum of nascent chains, indicating that ribosome pausing can also occur in intact cells. However, the cellular pause products were cotranslationally translocated. While endogenous apolipoprotein B-100 in HepG2 cells was fully translocated, discrete proteolytic fragments were generated from the amino terminus of the protein when proteases gained access to the lumen of permeabilized microsomes. These products were similar in size and sequence to apoliprotein B proteolytic fragments previously ascribed as the luminal domains of transmembrane apoB-100 molecules (Du, E. Z., Kurth, J., Wang, S. L., Humiston, P., and Davis, R. A. 1994. J. Biol. Chem. 269: 24169-24176).

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Leiper, Professor James
Authors: Leiper, J.M., Harrison, G.B., Bayliss, J., Scott, J.D., and Pease, R.J.
College/School:College of Medical Veterinary and Life Sciences > Institute of Cardiovascular and Medical Sciences
Journal Name:Journal of Lipid Research
Publisher:American Society for Biochemistry and Molecular Biology
ISSN:0022-2275
ISSN (Online):1539-7262

University Staff: Request a correction | Enlighten Editors: Update this record