Avian lens spectrin: subunit composition compared with erythrocyte and brain spectrin

• Published in: The Journal of cell biology 1983-10, Vol.97 (4), p.1271-1276
• Main Authors: Nelson, W.J, Granger, B.L, Lazarides, E
• Format: Article
• Language: English
• Subjects: Actins; Analytical, structural and metabolic biochemistry; animal physiology; Animals; Antibodies; Biological and medical sciences; Brain Chemistry; Cell membranes; Chickens; Cross Reactions; Epitopes; Erythrocytes; Erythrocytes - analysis; Fiber cells; Fundamental and applied biological sciences. Psychology; Gels; Glycoproteins; Immunoprecipitation; Lens, Crystalline - analysis; Microfilaments; Peptides - analysis; Plasma spectra; Proteins; Rapid Communications; Solubility; Spectrin - analysis; Spectrin - immunology
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.97.4.1271

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, Mr240,000 (lens α-spectrin), co-migrates with erythrocyte and brain α-spectrin on one- and two-dimensional SDS polyacrylamide gels and cross-reacts with antibodies specific for chicken erythrocyte α-spectrin; the smaller polypeptide, Mr235,000 (lens γ-spectrin), co-migrates with brain γ-spectrin and does not cross-react with either the α-spectrin antibodies or antibodies specific for chicken erythrocyte β-spectrin. Minor amounts of polypeptides antigenically related to erythrocyte β-spectrin with a greater electrophoretic mobility than lens γ-spectrin are also detected in lens. The equimolar ratio of lens α- and γ-spectrin is invariantly maintained during the extraction of lens plasma membranes under different conditions, or after immunoprecipitation of whole extracts of lens with erythrocyte α-spectrin antibodies. Two-dimensional peptide mapping reveals that whereas α-spectrins from chicken erythrocytes, brain, and lens are highly homologous, the γ-spectrins, although related, have some cell-type-specific peptides and are substantially different from erythrocyte β-spectrin. Thus, the expression of cell-type-specific γ- and β-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.