title: Biochemical and physicochemical properties of the solubilized S-100 protein binding activity of synaptosomal particulate fractions.
abstract: The 125I-labeled S-100 specific binding to a Triton X-100 (TX-100) extract of synaptosomal particulate fractions (SYN) was investigated. The results indicate that (a) S-100 binding to the TX-100 extract is partially irreversible after a critical association time at 37 degrees C, while it is fully reversible after any association time at 4 degrees C; (b) trypsin and phospholipase C partially reverse the S-100 binding, while phospholipase D enhances the interaction to some extent, in a dose-dependent way; (c) EDTA and high concentrations of NaCl or KCl are more efficient as inhibitors of the S-100 binding to the TX-100 extract than as 125I-labeled S-100 dissociating agents, in analogy with previous observations with SYN; and (d) two main populations of solubilized S-100 binding sites can be evidenced by gel filtration and sucrose gradient centrifugation when low amounts of the TX-100 extract are processed and/or low S-100 concentrations are used, while two additional molecular species are separated when greater amounts of either factors are tested. These results suggest the possibility that S-100 may be involved in the regulation of some membrane activities.
mesh_terms: D000818:Animals; D002499:Centrifugation, Density Gradient; D002540:Cerebral Cortex / Q000378:metabolism*; D002850:Chromatography, Gel; D017830:Octoxynol; D011092:Polyethylene Glycols / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D009418:S100 Proteins / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism; D013574:Synaptosomes / Q000378:metabolism*
chemical_list: D009418:S100 Proteins; D011092:Polyethylene Glycols; D017830:Octoxynol