Photoaffinity labeling sites

Greenberger, L.M. (1993) Major photoaffinity labeling sites for iodoaryl azidoprazosin in P-glycoprotein are within or immediately C-terminal to transmembrane domains 6 and 12. The Journal of Biological Chemistry, 268, 11417-11425. 

Sasaki, T, Shimazawa, R., Sawada, T., Iijima T, Fukasawa, H, Shudo, K, Hashimoto, Y, and Iwasaki, S. (1996) Location of two photoaffinity-labeled sites on the ligand-binding domain of retinoic acid receptor a. Biol. Pharm. Bull 19, 659-664. 

Photoaffinity labeling can be particularly useful when dealing with noncompetitive inhibitors, where the site of binding cannot be inferred from competition with specific substrate or cofactor molecules. 

In addition to its interaction with central BZD receptors, pharmacological concentrations of melatonin can also bind to the peripheral-type BZ receptors (PBRs), which are involved in neurosteroidogenesis (Garcia-Ovejero et al. 2005). PBRs are primarily localized on the outer mitochondrial membrane these sites are therefore also referred to as mitochondrial BZD receptors. Using the isoquinoline carboxamide, PK14105, for photoaffinity labelling, an 18 kDa isoquinoline... 

Galardy, R.E., Craig, L.C., Jamieson, J.D., and Printz, M.P. (1974) Photoaffinity labeling of peptide hormone binding sites./. Biol. Chem. 249, 3510-3518. 

Schmitt, M., Painter, R.G., Jesaitis, A.J., Preissner, K., Sklar, L.A., and Cochrane, C.G. (1983) Photoaffinity labeling of the N-formyl peptide receptor binding site of intact human polymorphonuclear leukocytes./. Biol. Chem. 258, 649-654. 

Duncalfe, L. L Carpenter, M. R Smillie, L. B Martin, I. L and Dunn, S. M. (1996) The major site of photoaffinity labeling of the gamma-aminobutyric acid type A receptor by [3H]flunitrazepam is histidine 102 of the alpha subunit../. Biol. Chem. 271,9209-9214. 

Middleton RE, Cohen JB. 1991. Mapping of the acetylcholine binding site of the nicotinic acetylcholine receptor [ H] nicotine as an agonist photoaffinity label. Biochemistry 30 6987-6997. 

Varela, I. Nimmo, H.G. Photoaffinity labelling shows that Escherichia coli isocitrate dehydrogenase kinase/phosphatase contains a single ATP-binding site. FEBS Lett., 231, 361-365 (1988)... 

Photochemically reactive molecules have often been used as labels for specific sites in proteins and nucleic acids. Psoralen derivatives serve as relatively nonspecific photochemically activated crosslinking agents for DNA and double-stranded RNA.195 Aryl azides are converted by light to aryl nitrenes, which react in a variety of ways including insertion into C-H bonds (Eq. 23-27).200 201 In some cases UV irradiation can be used to join natural substrates to enzymes or hormones to receptors. For example, progesterone, testosterone, and other steroids have been used for direct photoaffinity labeling of their receptors.202 Synthetic benzophenones have also been used widely as photoactivated probes.203... 

Scheme 2 Photoaffinity Labeling and Identification of a Ligand-Contact Site...

The photoaffinity labels have been useful in mapping out residues at the active sites of enzymes and the binding sites of proteins such as antibodies. The normal affinity labels are more useful for kinetic work, since they are selective for the basic and nucleophilic groups that are so prevalent in catalysis, and since they also give information on the pATfl s of the groups that are modified. 

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