A regulatory protein for orthophosphate-regulated cyclic phosphodiesterase in Neurospora crassa

A regulatory protein for orthophosphate-regulated cyclic phosphodiesterase (cPDase) was detected in mycelial extracts of Neurospora crassa. The protein, designated neucrassin, was precipitated by ammonium sulfate between 60 to 100% saturation, and fractionated by gel filtration through a TSK-gel column. The molecular weight was estimated to be 65,000. Neucrassin inhibited the hydrolyzing activity of cPDase for cyclic 3',5'-AMP in the presence of MnCl2 in a noncompetitive manner, whereas it stimulated the activity for cyclic 2',3'-AMP over a wide ranges of pH's, between 2.8 to 6.8.