Cocquerel Laurence, Op de Beeck Anne, Lambot Michel, Roussel Juliette, Delgrange David, Pillez André, Wychowski Czeslaw, Penin François, Dubuisson Jean
CNRS-UPR2511, Institut de Biologie de Lille and Institut Pasteur de Lille, 1 rue Calmette, BP447, 59021 Lille Cedex, France.
EMBO J. 2002 Jun 17;21(12):2893-902. doi: 10.1093/emboj/cdf295.
Hepatitis C virus proteins are synthesized as a polyprotein cleaved by a signal peptidase and viral proteases. The behaviour of internal signal sequences at the C-terminus of the transmembrane domains of hepatitis C virus envelope proteins E1 and E2 is essential for the topology of downstream polypeptides. We determined the topology of these transmembrane domains before and after signal sequence cleavage by tagging E1 and E2 with epitopes and by analysing their accessibility in selectively permeabilized cells. We showed that, after cleavage by signal peptidase in the endoplasmic reticulum, the C-terminal orientation of these transmembrane domains changed from luminal to cytosolic. The dynamic behaviour of these transmembrane domains is unique and it is linked to their multifunctionality. By reorienting their C-terminus toward the cytosol and being part of a transmembrane domain, the signal sequences at the C-terminus of E1 and E2 contribute to new functions: (i) membrane anchoring; (ii) E1E2 heterodimerization; and (iii) endoplasmic reticulum retention.
丙型肝炎病毒蛋白以多聚蛋白形式合成，该多聚蛋白由信号肽酶和病毒蛋白酶切割。丙型肝炎病毒包膜蛋白E1和E2跨膜结构域C末端内部信号序列的行为对于下游多肽的拓扑结构至关重要。我们通过用表位标记E1和E2并分析它们在选择性通透细胞中的可及性，确定了信号序列切割前后这些跨膜结构域的拓扑结构。我们发现，在内质网中被信号肽酶切割后，这些跨膜结构域的C末端方向从腔面变为胞质面。这些跨膜结构域的动态行为是独特的，并且与它们的多功能性相关。通过将其C末端重新定向至胞质溶胶并作为跨膜结构域的一部分，E1和E2 C末端的信号序列促成了新的功能：（i）膜锚定；（ii）E1E2异源二聚化；以及（iii）内质网滞留。
