Identification and structural characterization of an lyt-2/3 homolog in tunicates

Abstract

1. 1. A serologic and structural homolog to murine Lyt-2/3 molecular complex was sought in tunicate hemocytes by using monoclonal antibody specific Lyt-2 framework determinants (mAb 53-6.7). 2. 2. This antibody labeled a distinct population of tunicate hemocytes, as determined in indirect immunofluorescence and FACS analysis, and immunoprecipitated disulfide-bonded subunits from hemocytes equivalent to the 38 kDa (α), 34 kDa (α′) and 30 kDa (β) subunits of murie Lyt-2/3 molecules. 3. 3. As in mice, tunicate α- and α′-subunits each appeared to bear three N-linked oligosaccharides, one high mannose- and two complex-type glycans and focused as a number of heterogeneous spots on IEF gels. 4. 4. In contrast, β-subunits of both species were associated with a single N-linked glycan of the complex type and focused as basic components of limited charge heterogeneity. 5. 5. Based on tryptic peptide patterns, α, and α′-subunits, but not β-subunits, are likely to be structurally similar in both tunicate and mouse complexes. 6. 6. However, CNBr cleavage patterns indicated that the α-subunit of both species may differ in the size-location of the intrachain disulfide bridge. 7. 7. Collectively our observations suggest the phylogenetic emergence of an Lyt-2/3 homolog at an early level of evolution.