title: Changing pattern of cyclic AMP-binding proteins during germination of Mucor racemosus sporangiospores.
abstract: Interation of cyclic AMP with a profoundly changing pattern of specific binding proteins was shown during aerobic germination of sporangiospores from the fungus Mucor racemosus. 32P-labeled 8-azido-cycli AMP, an analogue of cyclic AMP that forms a covalent linkage with the binding proteins under u.v. light, was used as the ligand. Binding proteins carrying this photoaffinity label were separated by polyacrylamide-gel electrophoresis and identified by radioautography. Equibiltrium dissociation constants (Kd) and binding-response curves in the presence of competing nucleotides were identical for both 8-azido-cyclic [32P]AMP and cyclic [3H]AMP. A quantitative binding assay with both 8-azido-cyclic [32P]AMP and cyclic [3H]AMP over the time course of sporangiospore germination indicated a parallel relationship between cyclic AMP-binding capacity and the intracellular concentrations of cyclic AMP reported in a previous study [Paznokas & Sypherd (1975) J. Bacteriol. 124, 134--139]. Both of these parameters attained transient high values at a time of development when addition of exogenous cyclic AMP prevents hyphal-germ-tube emergence. The measured Kd values did not change during sport germination.
mesh_terms: D000345:Affinity Labels; D002352:Carrier Proteins / Q000378:metabolism*; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D007700:Kinetics; D009024:Morphogenesis; D009089:Mucor / Q000378:metabolism / Q000502:physiology*; D013172:Spores, Fungal / Q000378:metabolism
chemical_list: D000345:Affinity Labels; D002352:Carrier Proteins; D000242:Cyclic AMP