Identification of the CD45-associated 116-kDa and 80-kDa proteins as the alpha- and beta-subunits of alpha-glucosidase II.
CD45 is an abundant, highly glycosylated transmembrane protein-tyrosine phosphatase expressed on hematopoietic cells. Herein we demonstrate that two proteins of 116 kDa and 80 kDa copurify with CD45 from mouse T cells. Microsequence analysis of the 116-kDa protein revealed high similarity to an incomplete human open reading frame that has been suggested to correspond to the catalytic alpha-subunit of glucosidase II. We determined the nucleotide sequence of the mouse cDNA and observed that it encodes a protein product nearly identical to its human homologue and shares an active site consensus sequence with Family 31 glucosidases. Amino acid sequencing of the 80-kDa protein, followed by molecular cloning, revealed high homology to human and bovine cDNAs postulated to encode the beta-subunit of glucosidase II. Antisera developed to the mouse beta-subunit allowed us to demonstrate that the interaction between CD45 and glucosidase II can be reconstituted in vitro in an endoglycosidase H-sensitive manner. The strong interaction between glucosidase II and CD45 may provide a paradigm for investigating novel aspects of the biology of these proteins.
Arendt
C W
CW
Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta T6G 2H7, Canada.
Ostergaard
H L
HL
D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D006801:Humans; D017493:Leukocyte Common Antigens / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D011506:Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017421:Sequence Analysis; D013601:T-Lymphocytes / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D000520:alpha-Glucosidases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
D011506:Proteins; D017493:Leukocyte Common Antigens; C034251:4-nitrophenyl-alpha-glucosidase; D000520:alpha-Glucosidases