Membrane topology of coronavirus E protein.
Coronavirus small envelope protein E has two known biological functions: it plays a pivotal role in virus envelope formation, and the murine coronavirus E protein induces apoptosis in E protein-expressing cultured cells. The E protein is an integral membrane protein. Its C-terminal region extends cytoplasmically in the infected cell and in the virion toward the interior. The N-terminal two-thirds of the E protein is hydrophobic and lies buried within the membrane, but its orientation in the lipid membrane is not known. Immunofluorescent analyses of cells expressing biologically active murine coronavirus E protein with a hydrophilic short epitope tag at the N-terminus showed that the epitope tag was exposed cytoplasmically. Immunoprecipitation analyses of the purified microsomal membrane vesicles that contain the same tagged E protein revealed the N-terminal epitope tag outside the microsomal membrane vesicles. These analyses demonstrated that the epitope tag at the N-terminus of the E protein was exposed cytoplasmically. Our data were consistent with an E protein topology model, in which the N-terminal two-thirds of the transmembrane domain spans the lipid bilayer twice, exposing the C-terminal region to the cytoplasm or virion interior.
Department of Microbiology and Immunology, University of Texas Medical Branch at Galveston, Galveston, Texas 77555, USA.
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Makino
D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000821:virology*; D007150:Immunohistochemistry; D051379:Mice; D008861:Microsomes / Q000378:metabolism; D006517:Murine hepatitis virus / Q000737:chemistry / Q000378:metabolism*; D011233:Precipitin Tests; D014759:Viral Envelope Proteins / Q000302:isolation & purification / Q000378:metabolism*; D016662:Virus Integration
D014759:Viral Envelope Proteins