A Long Acidic Domain Affects the Chromatographic Behaviour of a Neuronal Adaptor Protein on DEAE-Sepharose

Abstract

  The stepwise chromatographic behaviour on DEAE-Sepharose of rat Fe65, a neuronal protein, was tested, using as eluants KCl, CaCl₂, and MgCl₂. Assays by western blot showed that Fe65 was eluted by CaCl₂, at a ionic strength 20% lower than that of MgCl₂ or KCl. Interestingly, in the case of a truncated Fe65, lacking a glutamic acid rich region at the N-terminus, the ionic strengths of the various eluants were almost identical. These results suggested a possible inhibitory role of calcium ions in the binding of the protein to DEAE and a specific affinity of these ions for long acidic stretches.