ABSTRACT
PaulErhlich1introducedtheconceptof"receptor"nearlyacenturyago.Implicitinthisconcept isthatagenuinereceptorsatisfiestwocriteria.Bimbaumerandcolleagues2formalizedthesetwo criteriainthisway:"...ahormonereceptorisa[bifunctional]elementofatargetcellthatspecifically recognizesahormoneandis[directly]responsibleforinitiatingaso-calledhormoneresponse." Establishingthataproteinbindsahormoneinaspecificmannerconsistentwiththephysiologyof theorganismmeetsthefirstcriterion.Todothisisnotatrivialmatterandwewilldiscusshowthe techniqueofphotoaffinitylabeling(PhL)maybeusefulinthisendeavor.Specifically,wewillfocus onhowthistechnique,ifproperlyimplemented,canenabletheidentification,purification,and characterizationofauxin-bindingproteins(ABP)fromavarietyofplants.Theseproteinsconstitute amultitudeofauxintargets:auxineffluxanduptakecarriers,enzymesinvolvedinauxineconomy suchassyntheticandconjugatingenzymes,enzymesthatmetabolizeauxinsbothspecificallyand nonspecifically(e.g.,detoxificationenzymes),proteinsthatmightsequesterauxins,aswellasthe receptorsthatmediateauxinaction.
