title: Avian lens spectrin: subunit composition compared with erythrocyte and brain spectrin.
abstract: Chicken lens spectrin is composed predominantly of equimolar amounts of two polypeptides with solubility properties similar, but not identical, to erythrocyte spectrin. The larger polypeptide, Mr 240,000 (lens alpha-spectrin), co-migrates with erythrocyte and brain alpha-spectrin on one- and two-dimensional SDS polyacrylamide gels and cross-reacts with antibodies specific for chicken erythrocyte alpha-spectrin; the smaller polypeptide, Mr 235,000 (lens gamma-spectrin), co-migrates with brain gamma-spectrin and does not cross-react with either the alpha-spectrin antibodies specific for chicken erythrocyte beta-spectrin. Minor amounts of polypeptides antigenically related to erythrocyte beta-spectrin with a greater electrophoretic mobility than lens gamma-spectrin are also detected in lens. The equimolar ratio of lens alpha- and gamma-spectrin is invariantly maintained during the extraction of lens plasma membranes under different conditions, or after immunoprecipitation of whole extracts of lens with erythrocyte alpha-spectrin antibodies. Two-dimensional peptide mapping reveals that whereas alpha-spectrins from chicken erythrocytes, brain, and lens are highly homologous, the gamma-spectrins, although related, have some cell-type-specific peptides and are substantially different from erythrocyte beta-spectrin. Thus, the expression of cell-type-specific gamma- and beta-spectrins may be the basis for the assembly of a spectrin-plasma membrane complex whose molecular composition is tailored to the functional requirements of the particular cell-type.
mesh_terms: D000818:Animals; D001923:Brain Chemistry; D002645:Chickens; D003429:Cross Reactions; D000939:Epitopes; D004912:Erythrocytes / Q000032:analysis*; D007908:Lens, Crystalline / Q000032:analysis*; D010455:Peptides / Q000032:analysis; D012995:Solubility; D013049:Spectrin / Q000032:analysis* / Q000276:immunology
chemical_list: D000939:Epitopes; D010455:Peptides; D013049:Spectrin