Open AccessThe Catalytic Subunit of Dictyostelium cAMP‐Dependent Protein Kinase
Author(s) -
Etchebehere Lilian C.,
Bemmelen Miguel X. P.,
Anjard Christophe,
Traincard François,
Assemat Karine,
Reymond Christophe,
Veron Michel
Publication year - 1997
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1997.t01-2-00820.x
Subject(s) - protein subunit , protein kinase a , kinase , biochemistry , gene isoform , sequence motif , biology , chemistry , microbiology and biotechnology , gene
The C subunit of Dictyostelium cAMP‐dependent protein kinase (PKA) is unusually large (73 kDa) due to the presence of 330 amino acids N‐terminal to the conserved catalytic core. The sequence following the core, including a C‐terminal‐Phe‐Xaa‐Xaa‐Phe‐COOH motif, is highly conserved. We have characterized the catalytic activity and stability of C subunits mutated in sequences outside the catalytic core and we have analyzed their ability to interact with the R subunit and with the heat‐stable protein‐kinase inhibitor PKI. Mutants carrying deletions in the N‐terminal domain displayed little difference in their kinetic properties and retained their capacity to be inhibited by R subunit and by PKI. In contrast, the mutation of one or both of the phenylalanine residues in the C‐terminal motif resulted in a decrease of catalytic activity and stability of the proteins. Inhibition by the R subunit or by PKI were however unaffected. Sequence‐comparison analysis of other protein kinases revealed that a‐Phe‐Xaa‐Xaa‐Phe‐motif is present in many Ser/Thr protein kinases, although its location at the very end of the polypeptide is a particular feature of the PKA family. We propose that the presence of this motif may serve to identify isoforms of protein kinases.