title: Identification of two regions of beta G spectrin that bind to distinct sites in brain membranes.
abstract: This study analyzed the complex interactions of intact spectrin with bovine brain membranes by evaluating membrane associations of defined regions of beta G spectrin, the subunit responsible for high affinity membrane binding. Two regions of beta G spectrin were expressed in bacteria and demonstrated to contain fully functional binding site(s) for a subset of spectrin-binding sites in brain membranes depleted of peripheral proteins. One region, located near the NH2 terminus, was comprised of 106-residue repeats and required repeats 2-7 for full activity. The other binding domain was located at the COOH terminus, which is the most variable between beta G and beta R spectrins, is distinct from the 106-residue repeats, and contains a pleckstrin homology domain. NH2-terminal beta spectrin polypeptides interacted with a membrane site(s) that recognized both brain and erythrocyte isoforms of spectrin, was inhibited by calcium/calmodulin, and was not blocked by the COOH-terminal polypeptide. The COOH-terminal region associated with a membrane site(s) that was specific for brain spectrin, was not inhibited by calcium/calmodulin, and was not blocked by the NH2-terminal polypeptide. These observations demonstrate membrane association of spectrin with at least two independent sites, which differ with regard to regulation by calcium/calmodulin and in selectivity for spectrin isoforms.
authors.affiliation: Howard Hughes Medical Institute, Duke University Medical Center, Durham, North Carolina 27710.
authors.forename: L H
authors.initials: LH
authors.lastname: Davis
authors.forename: V
authors.initials: V
authors.lastname: Bennett
mesh_terms: D000818:Animals; D017487:Ankyrins / Q000378:metabolism; D001665:Binding Sites; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism*; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D066298:In Vitro Techniques; D010446:Peptide Fragments / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid; D013049:Spectrin / Q000737:chemistry / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D017487:Ankyrins; D010446:Peptide Fragments; D011994:Recombinant Proteins; D013049:Spectrin