title: The 4.1-like proteins of the bovine lens: spectrin-binding proteins closely related in structure to red blood cell protein 4.1.
abstract: The superficial cortical fiber cells of the bovine lens contain membrane-associated proteins of 150,000, 80,000, and 78,000 D that cross-react with antisera prepared against red blood cell (RBC) protein 4.1 (Aster, J. C., G. J. Brewer, S. M. Hanash, and H. Maisel, 1984, Biochem. J., 224:609-616). To further study their relationship to protein 4.1, these proteins were immunoprecipitated from detergent extracts of crude lens membranes with purified polyclonal and monoclonal anti-4.1 antibodies and resolved by SDS PAGE. The electrophoretic mobilities of the lens proteins of 80,000 and 78,000 D were found to be identical to bovine RBC protein 4.1a and protein 4.1b, respectively. One- and two-dimensional peptide mapping revealed that a high degree of structural homology exists among all three of the lens 4.1-like proteins and RBC protein 4.1a and protein 4.1b. Despite the large difference in apparent molecular mass, the 150,000-D lens protein showed only minor peptide map differences. A nitrocellulose filter overlay assay showed that all three of the lens 4.1-like proteins bind to RBC and lens spectrins. We conclude that the bovine lens contains proteins of 80,000 and 78,000 D that are highly similar to protein 4.1 in structure and functional capacity. Additionally, the lens also contains a 4.1 isomorph of 150 kD. Analogous to RBC protein 4.1, these proteins may function in the lens by promoting association of spectrin with actin and by playing a role in the coupling of lens cytoskeleton to plasma membrane.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D001798:Blood Proteins / Q000276:immunology / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D002417:Cattle; D002454:Cell Differentiation; D003429:Cross Reactions; D003598:Cytoskeletal Proteins; D007908:Lens, Crystalline / Q000166:cytology / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D008970:Molecular Weight; D009479:Neuropeptides; D010446:Peptide Fragments / Q000032:analysis; D011494:Protein Kinases / Q000378:metabolism; D013049:Spectrin / Q000378:metabolism*
chemical_list: D000911:Antibodies, Monoclonal; D001798:Blood Proteins; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; D009479:Neuropeptides; D010446:Peptide Fragments; C028841:erythrocyte membrane band 4.1 protein; C120557:erythrocyte membrane protein band 4.1-like 1; D013049:Spectrin; D011494:Protein Kinases