Synthesis and binding of (125I2)philanthotoxin-343, (125I2)philanthotoxin-343-lysine, and (125I2)philanthotoxin-343-arginine to rat brain membranes

Journal Article · Thu Aug 01 04:00:00 EDT 1991 · Journal of Medicinal Chemistry; (United States)

DOI:https://doi.org/10.1021/jm00112a012· OSTI ID:5229656

Goodnow, Jr, R A; Bukownik, R; Nakanishi, K; Usherwood, P N; Eldefrawi, A T; Anis, N A; Eldefrawi, M E ^[1]

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1. Columbia University, New York, New York (USA)

125I2-iodinated philanthotoxin-343 (PhTX-343), (125I2)PhTX-343-arginine, and (125I2)PhTX-343-lysine were synthesized and evaluated as probes for glutamate receptors in rat brain synaptic membranes. It was found that these probes were not specific for the glutamate receptors but may be useful for investigating the polyamine binding site. Filtration assays with Whatman GF/B fiber glass filters were unsuitable because the iodinated PhTX-343 analogues exhibited high nonspecific binding to the filters, thus hindering detection of specific binding to membranes. When binding was measured by a centrifugal assay, (125I2)PhTX-343-lysine bound with low affinity (KD = 11.4 {plus minus} 2 microM) to a large number of sites (37.2 {plus minus} 9.1 nmol/mg of protein). The binding of (125I2)PhTX-343-lysine was sensitive only to the polyamines spermine and spermidine, which displaced (125I2)PhTX-343-lysine with Ki values of (3.77 {plus minus} 1.4) x 10(-5) M and (7.51 {plus minus} 0.77) x 10(-5) M, respectively. The binding was insensitive to glutamate receptor agonists and antagonists. Binding results with (125I2)PhTX-343-arginine were similar to those of (125I2)-PhTX-343-lysine. Considering the high number of toxin binding sites (10000-fold more than glutamate) in these membranes and the insensitivity of the binding to almost all drugs that bind to glutamate receptors, it is evident that most of the binding observed is not to glutamate receptors. On the other hand, PhTX analogues with photoaffinity labels may be useful in the isolation/purification of various glutamate and nicotinic acetylcholine receptors; they could also be useful in structural studies of receptors and their binding sites.

• OSTI ID: 5229656
• Journal Information: Journal of Medicinal Chemistry; (United States), Journal Name: Journal of Medicinal Chemistry; (United States) Vol. 34:8; ISSN JMCMA; ISSN 0022-2623
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AFFINITY
AMINES
AMINO ACIDS
ANIMALS
ANTIGENS
ARGININE
BETA DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BODY
BRAIN
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CELL MEMBRANES
CENTRAL NERVOUS SYSTEM
CHEMICAL PREPARATION
CPB
DAYS LIVING RADIOISOTOPES
ELECTRON CAPTURE RADIOISOTOPES
GLUTAMIC ACID
INTERMEDIATE MASS NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LYSINE
MAMMALS
MATERIALS
MEMBRANE PROTEINS
MEMBRANES
NERVOUS SYSTEM
NUCLEI
ODD-EVEN NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANS
PROTEINS
RADIOISOTOPES
RATS
REACTION KINETICS
RECEPTORS
RODENTS
SPERMIDINE
SPERMINE
SYNTHESIS
TOXIC MATERIALS
TOXINS
TRACER TECHNIQUES
VERTEBRATES