Structural analysis of the hinge region of fungal regulatory subunits of cAMP dependent protein kinase

RINALDI, J., ROSSI, S. AND MORENO, S.

San Francisco, California, USA

Congreso; Experimental Biology 2005; 2005

ASBMB

There are great differences among species in the affmity between regulatory(R) and cataIytic (C) subunits of cAMP dependent protein kinase. These differences can not be explained by the present structural data. Despite the high grade of sirnilarity among different R subunit sequences in general terms, there is striking sequence diversity in the hinge regióÍÍ. The airn of this workis to test if the hinge region interacts with C and if it can account for the differences observed among species in the R-C affmity. We studied the effects of several peptides on the phosphorylating activity of Mucor rouxii, Saccharomyces cerevisiae and bovine heart C subunits. The peptide sequences correspond to the autophosphory1ation site plus a variable region toward the amino termini of M rouxii and S. cerevisiae R subunits (between residues -41 and +4). Results show for the 3 enzymes that the longer the peptides, the higher their VMAX and the lower, their Km. No apparent significant difference was observed between M rouxii and S. cerevisiae peptides. We conclude that the R region studied participates in the interaction and does not account for the difference observed in the R-C affmity among species. These results taken as a whole suggest that noncatalytic domains outside the active cleft regulate the phosphorylating activity of C by the interaction with peptides derived ITom R sequence.