Homology of cytotoxic protein of eosinophilic leukocytes with IgE receptor Fc epsilon RII: implications for its structure and function.
The major protein constituent of eosinophilic leukocyte granules is a cytotoxic protein that plays a key role in antiparasitic defence mechanisms and immune hypersensitivity reactions. We show here that the protein is homologous with animal lectins; it exhibits greatest similarity to the lectin domain of the low-affinity IgE receptor of lymphocytes. On the basis of homology with lectins the disulphide bond pattern of the protein is predicted. It is proposed that certain cysteines unique to major basic protein are on the surface of the molecule and are involved in forming disulphide-bonded polymers. Homology with IgE receptor raises the possibility that major basic protein may also bind to IgE antibodies. Such an interaction could provide an efficient way of targeting the cytotoxic protein to parasites and allergens recognized by IgE antibodies.
Patthy
L
L
Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, Budapest.
D000595:Amino Acid Sequence; D000944:Antigens, Differentiation, B-Lymphocyte / Q000502:physiology*; D001798:Blood Proteins / Q000502:physiology*; D047091:Eosinophil Granule Proteins; D004804:Eosinophils / Q000276:immunology*; D006801:Humans; D037102:Lectins; D008969:Molecular Sequence Data; D011961:Receptors, Fc / Q000502:physiology*; D017455:Receptors, IgE; D012260:Ribonucleases; D013329:Structure-Activity Relationship
D000944:Antigens, Differentiation, B-Lymphocyte; D001798:Blood Proteins; D047091:Eosinophil Granule Proteins; D037102:Lectins; D011961:Receptors, Fc; D017455:Receptors, IgE; D012260:Ribonucleases