A cyclic AMP binding-protein from barley seedlings

Abstract

A protein fraction extracted from barley seedlings was shown to bind 3′:5′-cyclic AMP. The binding effect is real and not due to interference with the standard binding-protein assay used. Evidence is presented that this is a specific binding-protein; even at high concentrations other protein fractions from the same source showed no affinity for cyclic AMP. None of a range of cyclic and non-cyclic nucleotides that were examined exhibited a degree of binding with the protein comparable to that with cyclic AMP. The cyclic AMP/binding protein complex has a K d of 8 nM. This complex eluted at an identical position in the elution sequence from a Sephadex G-150 column as the uncomplexed binding-protein. The barley binding-protein is in a fraction which also exhibits the enzymic activities of glucose 6-phosphatase, ATPase, 5′-nucleotidase, and fructose 1,6-diphosphatase.