Characterization of human lactoferricin as a potent protein kinase CK2 activator regulated by A-kinase in vitro.
Lactoferricin (LFcin) hydrolyzed from lactoferrin (LF), a major 80 kDa iron-binding protein in milk and other exocrine secretions, was characterized as a potent activator of protein kinase CK2 (CK2) in vitro. Human LFcin (hLFcin) at 0.5 microg stimulated approx. 5-fold CK2 activity [phosphorylation of 60S acidic ribosomal proteins (P0, P1, P2) and Hsp90 (p98)] in a manner similar to other functional proteins with oligo-Arg clusters, such as salmine A1, sperm histone H2B and HIV-1 Rev. Interestingly, this stimulatory effect of hLFcin was significantly reduced when it was phosphorylated by A-kinase in vitro. These results suggest that (i) hLFcin acts as a potent CK2 activator in vitro; and (ii) the stimulatory effect of hLFcin on CK2 activity is regulated by its phosphorylation by A-kinase in vitro.
Maekawa
Toshiro
T
Laboratory of Genetical Biochemistry and Signal Biology, Graduate School of Medical Sciences, Kitasato University, Sagamihara, Japan.
Fujihara
Michio
M
Ohtsuki
Kenzo
K
D000595:Amino Acid Sequence; D000818:Animals; D047390:Casein Kinase II; D020536:Enzyme Activators / Q000494:pharmacology*; D006801:Humans; D007781:Lactoferrin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D008099:Liver / Q000187:drug effects / Q000201:enzymology; D008969:Molecular Sequence Data; D010455:Peptides / Q000032:analysis; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000302:isolation & purification / Q000378:metabolism*; D012269:Ribosomal Proteins / Q000378:metabolism; D013552:Swine
D020536:Enzyme Activators; D010455:Peptides; D012269:Ribosomal Proteins; C082171:lactoferricin B; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases; D007781:Lactoferrin