Expression of a Cell Surface Immobilization Antigen During Serotype Transformation in Tetrahymena thermophila

Abstract

A temperature shift from 40 to 28°C rapidly induced expression of a specific immobilization antigen at the cell surface in Tetrahymena thermophila. This transformation was inhibited by actinomycin D and cycloheximide but not by colchicine or cytochalasin B. The major surface antigen expressed at 28°C in cells homozygous for the SerH3 allele was partially purified, and an antiserum against this preparation was raised in rabbits. Electrophoresis, immunoblot, and [³⁵S]methionine incorporation studies are reported which support the conclusion that the H3 antigen is an acidic protein with an M_r of ~52,000 daltons. An induced synthesis of the H3 immobilization antigen was detected within 30 min after a shift from 40 to 28°C. This protein appeared to be synthesized in the microsomal fraction and transferred without cleavage to the cell surface, where it was inserted first into nonciliated regions.