Structural Analysis Of The Hinge Region Of Fungal Regulatory Subunits Of cAMP Dependent Protein Kinase.

JIMENA RINALDI; SILVIA ROSSI; SILVIA MORENO

San Diego, USA

Congreso; Experimental Biology 2005; 2005

ASBMB

Structural Analysis Of The Hinge Region Of Fungal Regulatory Subunits Of cAMP Dependent Protein Kinase. Jimena Rinaldi1, Silvia Rossi1 & Silvia Moreno1: Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires. There are great differences among species in the affinity between regulatory (R) and catalytic (C) subunits of cAMP dependent protein kinase. These differences can not be explained by the present structural data. Despite the high grade of similarity among different R subunit sequences in general terms, there is striking  sequence diversity in the hinge region. The aim of this work is to evaluate if the hinge region is a region of interaction and if it can account for the differences observed among species in the R-C interaction. In order to do this 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 autophosphorylation 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 were the higher were their vMAX and the lower, their kM. No 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 affinity among species. These results altogether can be interpreted as noncatalytic domains outside the active cleft regulate the phosphorylating activity of C by the interaction with peptides derived from R sequence.