Model of a putative pore: the pentameric alpha-helical bundle of SARS coronavirus E protein in lipid bilayers.
The coronavirus responsible for the severe acute respiratory syndrome contains a small envelope protein, E, with putative involvement in host apoptosis and virus morphogenesis. To perform these functions, it has been suggested that protein E can form a membrane destabilizing transmembrane (TM) hairpin, or homooligomerize to form a TM pore. Indeed, in a recent study we reported that the alpha-helical putative transmembrane domain of E protein (ETM) forms several SDS-resistant TM interactions: a dimer, a trimer, and two pentameric forms. Further, these interactions were found to be evolutionarily conserved. Herein, we have studied multiple isotopically labeled ETM peptides reconstituted in model lipid bilayers, using the orientational parameters derived from infrared dichroic data. We show that the topology of ETM is consistent with a regular TM alpha-helix. Further, the orientational parameters obtained unequivocally correspond to a homopentameric model, by comparison with previous predictions. We have independently confirmed that the full polypeptide of E protein can also aggregate as pentamers after expression in Escherichia coli. This interaction must be stabilized, at least partially, at the TM domain. The model we report for this pentameric alpha-helical bundle may explain some of the permabilizing properties of protein E, and should be the basis of mutagenesis efforts in future functional studies.
Torres
Jaume
J
School of Biological Sciences, Nanyang Technological University, Singapore. jtorres@ntu.edu.sg
Parthasarathy
Krupakar
K
Lin
Xin
X
Saravanan
Rathi
R
Kukol
Andreas
A
Liu
Ding Xiang
DX
D000595:Amino Acid Sequence; D002462:Cell Membrane / Q000378:metabolism; D019281:Dimerization; D004926:Escherichia coli / Q000378:metabolism; D008051:Lipid Bilayers / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010649:Phenylalanine / Q000494:pharmacology; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D045473:Severe acute respiratory syndrome-related coronavirus / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014759:Viral Envelope Proteins / Q000737:chemistry* / Q000378:metabolism; D000086082:Viroporin Proteins
C501689:E protein, SARS coronavirus; D008051:Lipid Bilayers; D014759:Viral Envelope Proteins; D000086082:Viroporin Proteins; D010649:Phenylalanine