| RESEARCH |
Light illuminates cell-signaling pathway Using light as a switch, researchers have created a general method to rapidly activate a particular protein in a signal transduction pathway [J. Am. Chem. Soc., 124, 8220 (2002)]. Hagan P. Bayley, professor of medical biochemistry and genetics at Texas A&M University's Health Science Center; chemistry professor Richard S. Givens of the University of Kansas; and coworkers thiophosphorylated the activating threonine of the catalytic subunit of cAMP-dependent protein kinase with its physiological kinase. They then "caged" the activated kinase at the threonine thiophosphate with a photolabile 4-hydroxyphenacyl group. Kinase modified in this way retains only 5% of its activity. Upon photolysis with UV light, the uncaged kinase has a 15-fold gain in activity. Unlike previous methods developed by Bayley and others, the enzyme is caged directly at the activating phosphoryl residue and requires no mutagenesis. This makes it likely to be useful for studying a variety of signaling proteins, most of which are regulated by phosphorylation at threonine, serine, or tyrosine. Proteins caged in this way are also expected to be useful in biophysical studies because removal of the 4-hydroxyphenacyl group occurs less than a microsecond after absorption of a photon. |
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