Studying the Dynamics of Ligand–Receptor Complexes by Single-Molecule Techniques - Single Molecule Dynamics in Life Science - page 140

Table 7.1 (Continued)

Receptor Ligand Technique Receptor mobility and ligand binding properties Reference

cAMPR in Dictyostelium discoi-

deum cells

cAMP labeled with Cy3 SMI (TIRFM) Diffusion: Regulation of chemotactic signaling by receptor

mobility.

[41]

Binding: Studies of the time course of single uorescent

spots and release curves revealed different dissociation
kinetics at the anterior and posterior regions, with themain
fraction of bound ligands having k diss ¼ 1.1 s 1 and 0.4 s 1 ,

respectively. The difference derived from intrinsic cell
polarity was caused by altered interactions between the
receptor and functional G proteins rather than by receptor
phosphorylation. The GTP-dependent decrease in the
lifetime of bound cAMP molecules was related to func-
tional G proteins. It was postulated that tight association of
the receptor and G protein stabilizes agonist binding.

C-peptide receptor in several Human C-peptide and insu- FCS Diffusion: Two populations of ligand receptor complexes [137]

-

human cell types lin labeled with

tetramethylrhodamine

with different mobility.

Binding: C-peptide binding isotherm yielded two binding
processes: a low af nity with stoichiometry 1:1 (n ¼ 1), and

possibly a high af 1. Time-

dependent displacement showed a single dissociation rate
constant of k diss ¼

nity (K d < 0.3 nM) with n <

10 4 s 1 . The results suggest the
existence of at least two different complexes: one of low
af

4.5 ·

nity and low
mobility. Pertussis toxin abolished binding indicating that
C-peptide binds to a GPCR.

nity and high mobility and one of high af