Evolution of CASK into a Mg2+-sensitive kinase.
All known protein kinases, except CASK [calcium/calmodulin (CaM)-activated serine-threonine kinase], require magnesium ions (Mg(2+)) to stimulate the transfer of a phosphate from adenosine 5'-triphosphate (ATP) to a protein substrate. The CaMK (calcium/calmodulin-dependent kinase) domain of CASK shows activity in the absence of Mg(2+); indeed, it is inhibited by divalent ions including Mg(2+). Here, we converted the Mg(2+)-inhibited wild-type CASK kinase (CASK(WT)) into a Mg(2+)-stimulated kinase (CASK(4M)) by substituting four residues within the ATP-binding pocket. Crystal structures of CASK(4M) with and without bound nucleotide and Mn(2+), together with kinetic analyses, demonstrated that Mg(2+) accelerates catalysis of CASK(4M) by stabilizing the transition state, enhancing the leaving group properties of adenosine 5'-diphosphate, and indirectly shifting the position of the gamma-phosphate of ATP. Phylogenetic analysis revealed that the four residues conferring Mg(2+)-mediated stimulation were substituted from CASK during early animal evolution, converting a primordial, Mg(2+)-coordinating form of CASK into a Mg(2+)-inhibited kinase. This emergence of Mg(2+) sensitivity (inhibition by Mg(2+)) conferred regulation of CASK activity by divalent cations, in parallel with the evolution of the animal nervous systems.
Mukherjee
Konark
K
Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 1050 Arastradero Road, Palo Alto, CA 94304, USA. konark@brandeis.edu
Sharma
Manu
M
Jahn
Reinhard
R
Wahl
Markus C
MC
Südhof
Thomas C
TC
D055162:Biocatalysis; D002460:Cell Line; D019143:Evolution, Molecular; D006801:Humans; D008274:Magnesium / Q000378:metabolism*; D008958:Models, Molecular; D010802:Phylogeny; D011487:Protein Conformation; D011494:Protein Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D011494:Protein Kinases; D008274:Magnesium