The association of the C-terminal region of beta I sigma II spectrin to brain membranes is mediated by a PH domain, does not require membrane proteins, and coincides with a inositol-1,4,5 triphosphate binding site.
The beta spectrin genes each produce two alternate transcripts the longer of which has a approximately 210 amino acid C-terminal extension including a pleckstrin homology (PH) domain and also an uncharacterized membrane binding site. GST constructs including the entire or the N-terminal segment of the beta I sigma II spectrin PH domain bind to crude and extracted brain membranes, to protein free brain lipid and to vesicles containing phosphatidylinositol-4,5-bisphosphate. This PH domain also binds radiolabelled inositol-1,4,5-trisphosphate (IP3) and preincubation with IP3 inhibits binding to extracted brain membranes. We conclude that membrane binding of the beta I sigma II spectrin C-terminal region is by means of a direct interaction between the N-terminal region of the PH domain and membrane lipids and does not require membrane protein. The PH domain of the beta-adrenergic receptor kinase showed different binding properties in every assay employed, showing that different PH domains may have different membrane binding specificity.
Wang
D S
DS
University of Florida College of Medicine, Department of Neuroscience, Gainesville 32610, USA.
Shaw
G
G
D000818:Animals; D001665:Binding Sites; D001798:Blood Proteins / Q000737:chemistry; D001921:Brain / Q000378:metabolism* / Q000648:ultrastructure; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism*; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D010750:Phosphoproteins; D011994:Recombinant Proteins; D013049:Spectrin / Q000378:metabolism*
D001798:Blood Proteins; D008565:Membrane Proteins; D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates; D010750:Phosphoproteins; D011994:Recombinant Proteins; C039077:platelet protein P47; D013049:Spectrin; D015544:Inositol 1,4,5-Trisphosphate