Stable interdomain interaction within the cytoplasmic domain of CD45 increases enzyme stability.
CD45 is a leukocyte-specific, two domain transmembrane tyrosine phosphatase. Co-purification of a recombinant protein containing the first phosphatase domain of CD45 (6His-D1) with a recombinant protein containing the second phosphatase domain (GST-D2) from E. coli indicated a stable interaction which resulted in increased stability of the active phosphatase domain present in 6His-D1. This interaction was not dependent on the acidic region unique to CD45 domain 2, but was affected by a destabilizing point mutation (Q1180G) in GST-D2. CD45 domain 2 enhanced phosphatase activity of the first domain in the full length cytoplasmic domain protein, whereas a chimeric protein with the SH2 domain of p56(lck) in place of the CD45 C-terminal region did not. Thus the C-terminal domain of CD45 associates with the N-terminal domain and this stabilizes the active phosphatase domain. A single destabilizing point mutation in the second domain is sufficient to attenuate this effect.
Felberg
J
J
Department of Microbiology, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada.
Johnson
P
P
D000818:Animals; D002384:Catalysis; D003593:Cytoplasm / Q000737:chemistry*; D004591:Electrophoresis, Polyacrylamide Gel; D004795:Enzyme Stability; D005982:Glutathione Transferase / Q000378:metabolism; D007700:Kinetics; D017493:Leukocyte Common Antigens / Q000737:chemistry* / Q000235:genetics; D051379:Mice; D009154:Mutation; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D011995:Recombination, Genetic; D015398:Signal Transduction; D013696:Temperature
D011993:Recombinant Fusion Proteins; D005982:Glutathione Transferase; D010744:Phosphoric Monoester Hydrolases; D017493:Leukocyte Common Antigens