Ca(2+) bridges the C2 membrane-binding domain of protein kinase Calpha directly to phosphatidylserine.
The C2 domain acts as a membrane-targeting module in a diverse group of proteins including classical protein kinase Cs (PKCs), where it plays an essential role in activation via calcium-dependent interactions with phosphatidylserine. The three-dimensional structures of the Ca(2+)-bound forms of the PKCalpha-C2 domain both in the absence and presence of 1, 2-dicaproyl-sn-phosphatidyl-L-serine have now been determined by X-ray crystallography at 2.4 and 2.6 A resolution, respectively. In the structure of the C2 ternary complex, the glycerophosphoserine moiety of the phospholipid adopts a quasi-cyclic conformation, with the phosphoryl group directly coordinated to one of the Ca(2+) ions. Specific recognition of the phosphatidylserine is reinforced by additional hydrogen bonds and hydrophobic interactions with protein residues in the vicinity of the Ca(2+) binding region. The central feature of the PKCalpha-C2 domain structure is an eight-stranded, anti-parallel beta-barrel with a molecular topology and organization of the Ca(2+) binding region closely related to that found in PKCbeta-C2, although only two Ca(2+) ions have been located bound to the PKCalpha-C2 domain. The structural information provided by these results suggests a membrane binding mechanism of the PKCalpha-C2 domain in which calcium ions directly mediate the phosphatidylserine recognition while the calcium binding region 3 might penetrate into the phospholipid bilayer.
Verdaguer
N
N
IBMB-CSIC, Jordi Girona Salgado 18,26, E-08034 Barcelona.
Corbalan-Garcia
S
S
Ochoa
W F
WF
Fita
I
I
Gómez-Fernández
J C
JC
D000595:Amino Acid Sequence; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D003001:Cloning, Molecular; D003198:Computer Simulation; D018360:Crystallography, X-Ray; D004926:Escherichia coli; D007527:Isoenzymes / Q000737:chemistry* / Q000378:metabolism*; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010718:Phosphatidylserines / Q000378:metabolism*; D011487:Protein Conformation; D011493:Protein Kinase C / Q000737:chemistry* / Q000378:metabolism*; D051571:Protein Kinase C-alpha; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism
C402786:1,2-dicaproylphosphatidylserine; D007527:Isoenzymes; D010718:Phosphatidylserines; D011994:Recombinant Proteins; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha; D002118:Calcium