The G-CSF-R mutants. (A) Schematic diagram of the cytoplasmic domains of the G-CSF-R proteins. Boxes 1, 2, and 3 denote subdomains conserved in several members of the hematopoietin receptor superfamily. ED, extracellular domain; TM, transmembrane domain; ID, intracellular domain; Y, tyrosine; F, phenylalanine. (B) Flow cytometric analysis of G-CSF-R expressio on 32D.C10 transfectants. Cells were either stained with biotinylated anti–G-CSF-R antibodies followed by PE-conjugated streptavidin (solid lines) or with PE-conjugated streptavidin alone (dotted lines).