Phosphorylation of tyrosine enhances its electron transfer capability: a model of redox modulation as oncogene expression?
The influence of tyrosine and o-phosphotyrosine on the transfer of electrons to nitrobluetetrazolium (NBT) was studied. Tyrosine phosphate was found to strongly promote the transfer of electrons from ferrous iron to NBT, while tyrosine was inhibitory. The enhancement of NBT reduction by tyrosine phosphate was blocked by superoxide dismutase (SOD). The results suggest a role for phosphorylated tyrosine residues to promote intracellular redox reactions. We suggest that the role of tyrosine protein kinases in cell proliferation and transformation may be to regulate electron transport in as yet undefined cellular systems. Consistent with a unique role for phosphotyrosine, the other commonly occurring phosphoamino acids, o-phosphoserine and o-phosphothreonine were not effective electron transfer agents.
Peterson
D A
DA
Research Service, Veterans Administration Medical Center, Minneapolis, Minnesota 55417.
Kelly
B
B
Butterfield
J
J
Ashley
J
J
Peterson
R
R
Gerrard
J M
JM
D004579:Electron Transport; D005296:Ferrous Compounds / Q000378:metabolism; D008956:Models, Chemical; D009580:Nitroblue Tetrazolium / Q000378:metabolism; D010084:Oxidation-Reduction; D010766:Phosphorylation; D019000:Phosphotyrosine; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism*
D005296:Ferrous Compounds; D019000:Phosphotyrosine; D009580:Nitroblue Tetrazolium; D014443:Tyrosine