Changing pattern of cyclic AMP-binding proteins during germination of Mucor racemosus sporangiospores

Publisher Website
Google Scholar
Abstract
Interaction of cyclic[c]AMP with a profoundly changing pattern of specific binding proteins was shown during aerobic germination of sporangiospores from the fungus M. racemosus. 32P-labeled 8-azido-cAMP, an analog of cAMP that forms a covalent linkage with the binding proteins under UV light, was used as the ligand. Binding proteins carrying this photoaffinity label were separated by polyacrylamide-gel electrophoresis and identified by radioautography. Equilibrium dissociation constants (Kd) and binding-response curves in the presence of competing nucleotides were identical for 8-azido-[32P]cAMP and [3H]cAMP. A quantitative binding assay with 8-azido-[32P]cAMP and [3H]cAMP over the time course of sporangiospore germination indicated a parallel relationship between cAMP-binding capacity and the intracellular concentrations of cAMP reported in a previous study. Both of these parameters attained transient high values at a time of development when addition of exogenous cAMP prevents hyphal-germ-tube emergence. The measured Kd values did not change during spore germination.