TY - JOUR
T1 - Folding of influenza hemagglutinin in the endoplasmic reticulum
AU - Braakman, Ineke
AU - Hoover-Litty, Helana
AU - Wagner, Krystn R.
AU - Helenius, Ari
PY - 1991/8
Y1 - 1991/8
N2 - The folding of influenza hemagglutinin (HAO) in the ER was analyzed in tissue culture cells by following the formation of intrachain disulfides after short (1 min) radioactive pulses. While some disulfide bonds were already formed on the nascent chains, the subunits acquired their final disulfide composition and antigenic epitopes posttranslationally. Two posttranslational folding intermediates were identified. In CHO cells constitutively expressing HA0, mature HAO subunits were formed with a half time of 3 min and their folding reached completion at 22 min. The rate of folding was highly dependent on cell type and expression system, and thus regulated by factors other than the sequence of the protein alone. Exposure of cells to stress conditions increased the level of glucose regulated proteins, including BiP, and decreased the folding rate. The efficiency of folding and subsequent trimerization was not dependent on the rate of translation, nor on temperature between 37 and 15°C; however, the rates of folding and trimerization decreased with decreasing temperature. Whereas the rate of folding was independent of expression level, trimerization was accelerated at higher levels of expression.
AB - The folding of influenza hemagglutinin (HAO) in the ER was analyzed in tissue culture cells by following the formation of intrachain disulfides after short (1 min) radioactive pulses. While some disulfide bonds were already formed on the nascent chains, the subunits acquired their final disulfide composition and antigenic epitopes posttranslationally. Two posttranslational folding intermediates were identified. In CHO cells constitutively expressing HA0, mature HAO subunits were formed with a half time of 3 min and their folding reached completion at 22 min. The rate of folding was highly dependent on cell type and expression system, and thus regulated by factors other than the sequence of the protein alone. Exposure of cells to stress conditions increased the level of glucose regulated proteins, including BiP, and decreased the folding rate. The efficiency of folding and subsequent trimerization was not dependent on the rate of translation, nor on temperature between 37 and 15°C; however, the rates of folding and trimerization decreased with decreasing temperature. Whereas the rate of folding was independent of expression level, trimerization was accelerated at higher levels of expression.
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U2 - 10.1083/jcb.114.3.401
DO - 10.1083/jcb.114.3.401
M3 - Article
C2 - 1650370
AN - SCOPUS:0025816663
SN - 0021-9525
VL - 114
SP - 401
EP - 411
JO - Journal of Cell Biology
JF - Journal of Cell Biology
IS - 3
ER -