title: Structural and functional relationship of red blood cell protein 4.1 to synapsin I.
abstract: It has been suggested that the neuron specific protein synapsin I is closely related to red blood cell (rbc) protein 4.1. A systematic comparison of the structural and functional properties of rbc protein 4.1 and synapsin I has been carried out. There is approximately a three order of magnitude difference in cross reactivity of synapsin I with rbc 4.1 antiserum vs. synapsin I antiserum, as determined by a competitive quantitative dot assay. Two-dimensional chymotryptic iodopeptide mapping analysis demonstrated limited peptide homology (approximately 34% spot overlap) between rbc 4.1 and synapsin I. Dephosphorylated synapsin I binds saturably to brain spectrin (240/235) with an estimated dissociation constant (Kd) of 700 nM and a maximal binding capacity of 4 mol synapsin I/mol spectrin tetramer, similar to the affinity and stoichiometry of 4.1 binding to rbc spectrin. Synapsin I was found to bind to the terminal ends of the brain spectrin tetramer by low-angle rotary shadowing, analogous to 4.1 binding to rbc spectrin. In summary, synapsin I is structurally and immunologically distinct from rbc 4.1, yet shares functional similarities with rbc 4.1 with respect to its spectrin binding characteristics.
authors.affiliation: Department of Physiology and Anatomy, Milton S. Hershey Medical Center, Pennsylvania State University, Hershey 17033.
authors.forename: K E
authors.initials: KE
authors.lastname: Krebs
authors.forename: S M
authors.initials: SM
authors.lastname: Prouty
authors.forename: I S
authors.initials: IS
authors.lastname: Zagon
authors.forename: S R
authors.initials: SR
authors.lastname: Goodman
mesh_terms: D000818:Animals; D001798:Blood Proteins / Q000032:analysis*; D002417:Cattle; D003429:Cross Reactions; D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins / Q000032:analysis*; D009479:Neuropeptides; D010449:Peptide Mapping; D013329:Structure-Activity Relationship; D016704:Synapsins; D009435:Synaptic Transmission
chemical_list: D001798:Blood Proteins; D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D009479:Neuropeptides; D016704:Synapsins; C028841:erythrocyte membrane band 4.1 protein; C120557:erythrocyte membrane protein band 4.1-like 1