Disulphide-linked receptors for IgE on rat basophilic leukaemia cells

Rat basophilic leukaemia (RBL) cells are known to possess three different kinds of receptors capable of interacting with IgE, which have been named R, H and 71K and which differ in apparent molecular weight (MW) as determined by SDS-PAGE. Reduction of receptors isolated from surface-iodinated RBL cells reduced the MW of 71K to a value corresponding to the MW of R without altering significantly the MW of H or R. Only a single reduction product of 71K could be detected when either surface-iodinated or 3H-leucine labelled RBL cells were used. Analysis of one- and two-dimensional tryptic peptide maps derived from surface-iodinated receptors revealed a similarity between R and 71K. The tryptic peptides of H exhibited an entirely different pattern. These results suggest that 71K consists either of two disulphide-linked R-like molecules, or of one such molecule linked to another as yet undetected polypeptide chain.