Conservation of four key amino acids of CHIKV E1 protein among 16 alphaviruses. Four amino acids (G91, V178, A226, and H230 shown in red and boxed) were investigated to characterize their role in E1 membrane fusion. Flanking amino acids are shown in three segments, segment 1: amino acids 83 to 101 containing the fusion peptide region, segment 2: amino acid 176 to 180, and segment 3: amino acid 225 to 231. Amino acids are shown with a single letter abbreviation, and the identical amino acid is shown as an asterisk. Abbreviations of viruses and GenBank accession numbers held by the National Center for Biotechnology Information Database are as follows: CHIKV, Chikungunya virus (AF369024); SFV, Semliki Forest virus (X04129); RRV, Ross River virus (M20162); ONN, O'Nyong-nyong virus (AF079456); SINV, Sindbis virus (P89913); EEE, Eastern equine encephalitis virus (Q9PZX1); NM, Ndumu virus (AAL35778); VEE, Venezuelan equine encephalitis virus (Q9YKC9); WEE, Western equine encephalitis virus (Q9IBP3); FM, Fort Morgan virus (Q80S49); WHAT, Whataroa virus (Q80S41); AURA, Aura virus (Q86925); SAGV, Sagiyama (AAO33337.1); BF, Barmah Forest virus (AAO33347), MAYA, Mayaro virus (AAO33335.1), and MIDD, Middleburg virus (AA033343.1).