Fig. 1.

Schematic representation of the Junín virus GP-C glycoprotein and N- and C-terminal heptad-repeat regions. (A) Amino acids of the Junín virus envelope glycoprotein are numbered from the initiating methionine, and cysteine residues (|) and potential glycosylation sites (Y) are marked. The SSP and SKI-1/S1P cleavage sites and the resulting SSP, G1 and G2 subunits are indicated. Within G2, the C-terminal transmembrane (TM) and cytoplasmic (cyto) domains are shown, as are the N- and C-terminal heptad-repeat regions (light gray shading). A comparison of heptad-repeat sequences among arenavirus species is detailed below. Sequences include the New World isolates Junín (D10072), Tacaribe (M20304), Machupo (AY129248) and Guanarito (AAN05423) and Old World isolates Lassa-Josiah (M15076), Mopeia (M33879), LCMV-Armstrong (M20869). The 3,4 periodicity of a and d heptad-repeat positions is indicated by shading. (B) Helical wheel projections of proposed heptad-repeat periodicity. Amino acids shown above are listed in numeric order at a–g positions. A schematic of a six-helix bundle is at the lower right, and the details of the canonical interhelical packing arrangement are illustrated.