Biology Reference
In-Depth Information
FIGURE 20.1
Dynamic equilibrium of a G protein-coupled receptor (GPCR) and a
glycosylphosphatidylinositol-anchored protein (GPI-AP) among monomers, dimers, and
oligomers. (A) TheGPCRN-formyl peptide receptor (FPR) forms transient dimers that have three
kinetic parameters: on rate, off rate, and two-dimensional association rate (2D-
K
D
). (B) GPI-APs
form transient homodimers stabilized by both protein-protein interactions and raft-lipid
interactions (left), whereas raft-lipid interactions alone without ectodomain protein interactions
barely induce GPI-AP heterodimers (right). Transmembrane proteins also form transient
homodimers via protein-protein interactions with shorter lifetimes (center).
Kusumi, 2007; Suzuki, Fujiwara, Sanematsu, et al., 2007
). All of these studies have
been performed by detecting the transient colocalization of two individual fluores-
cent spots of receptors or by measuring fluorescent intensities of individual spots in
living cell membranes.
This chapter describes a protocol for single-molecule imaging and analysis of
colocalizations of two individual fluorescent spots of receptors such as GPCRs
and GPI-APs. Single-molecule imaging is also a basic technique for superresolution
microscopies such as photoactivated localization microscopy (
Owen, Williamson,
