FIG. 1.

Amino acid changes selected during passage of chimeric SIN(RRE1) virus. (A) Diagram of the genome organization of SIN(RR6KE1) with an expanded view of the glycoprotein region below. SIN sequences are shaded dark gray, and RR sequence is shaded light gray. Transmembrane domains are shaded with diagonal hatching; the “stem” region of E1 is shaded with wavy lines. Residue numbers where variants mapped are indicated below the open reading frame, and the parental amino acid in each case is shown above. aa, amino acids. (B) Amino acid changes found in eight independent passage series. In most cases the changes found were shown to be representative of the variant population by sequencing two independent clones and finding the change in each clone or by sequencing the PCR DNA prior to cloning. For the changes shown in parentheses, only a single clone was sequenced and it is uncertain whether these changes are representative of the revertant population. A limited number of other changes were also observed that were clonal, that is, found only in one of two sequenced clones and that may have arisen by PCR mutagenesis during cloning. These changes are not shown because their origin is uncertain and because, in any event, they do not represent the consensus sequence of the variant population.