Cyclic adenosine 3',5'-monophosphate binding protein in developing myxospores of Myxococcus xanthus

The interaction of cyclic adenosine 3',5'-monophosphate (cAMP) with specific protein molecules was examined in the high-speed supernatant fraction of extracts made at stages throughout glycerol-induced myxospore development in Myxococcus xanthus. Experiments using 8-azido[32P]cAMP, a photoaffinity analogue of cAMP, and SDS - polyacrylamide gel electrophoresis showed that the nucleotide interacts with only a single protein band of 12 500 molecular weight. Both the identiy and amount of this protein remained constant throughout development. The binding protein was specific for cAMP; other nucleotides did not compete with cAMP for binding sites. A Scatchard analysis showed evidence of only a single class of binding sites with a high affinity for cAMP.