Figure 2.

SQV-3 is similar to members of a glycosyltransferase family. (A) Cosmid C47F11 and plasmid clones assayed for sqv-3 rescue activity. Symbols are used as in Fig. 1A. (B) Alignment of the SQV-3, GalT, GlcNAcT, and partial human N-acetylgalactosaminyltransferase (GalNAcT) protein sequences and a C. elegans protein sequence, W02B12.11, predicted by the Genome Sequencing Consortium. Identities, transmembrane domains, and predicted changes in mutant alleles are indicated as in Fig. 1B. Open arrowheads indicate Tyr and Trp residues in GalT implicated in binding GlcNAc and/or UDP-Gal, the black arrowhead indicates a Trp residue in GalT required for catalytic activity, and the gray arrowhead indicates a GalT Tyr residue that can be replaced by Phe without affecting catalytic activity (43). The long version of GalT is shown, and the initiator methionine of the short version is circled.