Colinear arrangement of similarities in Sindbis virus E1 and Sandfly fever virus Gc. Alignments were constructed as detailed in the text. Panel A: Linear arrangement of the domain structure of SIN E1 and proposed domain structure of SAN Gc according to the convention for class II viral fusion proteins (β-penetrenes) originally described for TBEV E by Rey et al. . Regions of significant sequence similarities in SIN E1 and SAN Gc determined by the PRSS3 sequence alignment program are indicated. Probabilities (p values) are based on 1000 shuffles. Panel B: Amino acids are numbered from the beginning of the Sindbis virus subgenonic mRNA encoded polyprotein and the beginning of the SAN M segment encoded polyprotein. (:) refers to identical amino acids. (.) refers to chemically similar amino acids. Plum amino acids: N-glycosylation sites. Hydrophobic transmembrane domains were predicted using TMpred. Sequences with significant WWIHS scores were identified by MPeX (olive). In SAN Gc, predicted α-helices are indicated by dashed boxes and predicted β-sheets are underlined with a dashed arrow.