The last five amino acid residues at the C-terminus of PRK1/PKN is essential for full lipid responsiveness.
PRK1/PKN is a member of the protein kinase C (PKC) superfamily of serine/threonine protein kinases. Despite its important role as a RhoA effector, limited information is available regarding how this kinase is regulated. We show here that the last seven amino acid residues at the C-terminus is dispensable for the catalytic activity of PRK1 but is critical for the in vivo stability of this kinase. Surprisingly, the intact hydrophobic motif in PRK1 is dispensable for 3-phosphoinositide-dependent kinase-1 (PDK-1) binding and phosphorylation of the activation loop, as the PRK1-Delta940 mutant lacking the last two residues of the hydrophobic motif and the last 5 residues at the C-terminus interacts with PDK-1 in vivo and has a similar specific activity as the wild-type protein. We also found that the last four amino acid residues at the C-terminus of PRK1 is critical for the full lipid responsiveness as the PRK1-Delta942 deletion mutant is no longer activated by arachidonic acid. Our data suggest that the very C-terminus in PRK1 is critically involved in the control of the catalytic activity and activation by lipids. Since this very C-terminal segment is the least conserved among members of the PKC superfamily, it would be a promising target for isozyme-specific pharmaceutical interventions.
Department of Biochemistry, Faculty of Medicine, The National University of Singapore, 8 Medical Drive, Room 2-5, MD4 Annex, Singapore 117597, Singapore.
Wee Guan
WG
Lim
Yimin
Y
Zhu
Chern-Hoe
CH
Wang
Bee Jen
BJ
Tan
Jeffrey S
JS
Armstrong
Terje
T
Dokland
Hongyuan
H
Yang
Yi-Zhun
YZ
Zhu
Tian Seng
TS
Teo
Wei
W
Duan
D064413:3-Phosphoinositide-Dependent Protein Kinases; D000595:Amino Acid Sequence; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D001224:Aspartic Acid / Q000737:chemistry; D019556:COS Cells; D002384:Catalysis; D002522:Chlorocebus aethiops; D004789:Enzyme Activation; D004795:Enzyme Stability; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010649:Phenylalanine / Q000737:chemistry; D011493:Protein Kinase C / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D017434:Protein Structure, Tertiary; D051381:Rats; D016415:Sequence Alignment
D016718:Arachidonic Acid; D001224:Aspartic Acid; D010649:Phenylalanine; C061570:protein kinase N; D064413:3-Phosphoinositide-Dependent Protein Kinases; D017346:Protein Serine-Threonine Kinases; D011493:Protein Kinase C