TY - JOUR
T1 - Use of a Nitrotryptophan-Containing Peptide for Photoaffinity Labeling the Pancreatic Cholecystokinin Receptor
AU - Klueppelberg, Ulrich G.
AU - Gaisano, Herbert Y.
AU - Powers, Stephen P.
AU - Miller, Laurence J.
PY - 1989/4/1
Y1 - 1989/4/1
N2 - We report the preparation and characterization of a new type of intrinsic photoaffinity labeling probe, on the basis of the incorporation of a photolabile nitrotryptophan into a biologically relevant domain of a peptide. The model system used was the pancreatic cholecystokinin (CCK) receptor, previously affinity labeled with a variety of probes. Those studies have suggested that an Mr= 85 000–95 000 protein is more likely to be labeled as the site of covalent attachment approaches the receptor-binding domain of this hormone. Indeed, CCK has a Trp in the center of its receptor-binding region, and replacement of that residue with 6-nitrotryptophan resulted in a photolabile probe which affinity labeled the same Mr = 85 000–95 000 pancreatic membrane protein. This probe, 125I-D-Tyr-Gly-[(Nle28'31,6-NO2-Trp30)CCK-26-33], was synthesized by solid-phase and solution techniques and characterized by mass spectrometry. Following oxidative iodination, it was purified on HPLC to 2000 Ci/mmol. Binding to pancreatic membranes was rapid, temperature dependent, reversible, saturable, and specific and was with high affinity (Kd = 3 nM). While its binding affinity was only 3-fold lower than that of native CCK-8, this probe was 70-fold less potent than native hormone in stimulating amylase secretion (EC50 = 1 nM) and equally efficacious to native hormone. Despite the slight decrease in affinity, this probe demonstrated a high relative efficiency of covalent labeling of the Mr= 85 000–95 000 protein. This confirms that the Mr = 85 000–95 000 protein represents the hormone-binding subunit of the CCK receptor and demonstrates the utility of this type of photoaffinity labeling probe. This should provide a generally applicable substitution for photoaffinity labeling of molecules in which a Trp resides in a domain relevant for the characterization of a bimolecular interaction.
AB - We report the preparation and characterization of a new type of intrinsic photoaffinity labeling probe, on the basis of the incorporation of a photolabile nitrotryptophan into a biologically relevant domain of a peptide. The model system used was the pancreatic cholecystokinin (CCK) receptor, previously affinity labeled with a variety of probes. Those studies have suggested that an Mr= 85 000–95 000 protein is more likely to be labeled as the site of covalent attachment approaches the receptor-binding domain of this hormone. Indeed, CCK has a Trp in the center of its receptor-binding region, and replacement of that residue with 6-nitrotryptophan resulted in a photolabile probe which affinity labeled the same Mr = 85 000–95 000 pancreatic membrane protein. This probe, 125I-D-Tyr-Gly-[(Nle28'31,6-NO2-Trp30)CCK-26-33], was synthesized by solid-phase and solution techniques and characterized by mass spectrometry. Following oxidative iodination, it was purified on HPLC to 2000 Ci/mmol. Binding to pancreatic membranes was rapid, temperature dependent, reversible, saturable, and specific and was with high affinity (Kd = 3 nM). While its binding affinity was only 3-fold lower than that of native CCK-8, this probe was 70-fold less potent than native hormone in stimulating amylase secretion (EC50 = 1 nM) and equally efficacious to native hormone. Despite the slight decrease in affinity, this probe demonstrated a high relative efficiency of covalent labeling of the Mr= 85 000–95 000 protein. This confirms that the Mr = 85 000–95 000 protein represents the hormone-binding subunit of the CCK receptor and demonstrates the utility of this type of photoaffinity labeling probe. This should provide a generally applicable substitution for photoaffinity labeling of molecules in which a Trp resides in a domain relevant for the characterization of a bimolecular interaction.
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U2 - 10.1021/bi00434a047
DO - 10.1021/bi00434a047
M3 - Article
C2 - 2742849
AN - SCOPUS:0024604460
SN - 0006-2960
VL - 28
SP - 3463
EP - 3468
JO - Biochemistry
JF - Biochemistry
IS - 8
ER -