Right - click to enlarge - Cartoon representation of a complex between DNA and the ZIF268 protein, containing 3 zinc finger motifs. The coordinating residues of the middle zinc finger are highlighted. Based on the x-ray structure of PDB 1A1L. Color coding: ZIF268: blue; DNA: orange; Zinc ions: green Author: Thomas Splettstoesser Download high-resolution version (1188x1114, 410 KB)
Receptor proteins are located in the cytoplasm, cell membrane, or nuclear membrane.
1. Cytoplasmic receptor proteins include those that respond to steroid hormones. Ligand activated receptors may enter the cell nucleus where they modulate gene expression.
2. Receptors within cell membranes may be peripheral or trans-membrane proteins. Many receptors for hormones and neurotransmission are trans-membrane proteins.
_a. Metabotropic receptors are coupled to G proteins, acting through various secondary pathways involving ion channels, enzymes such as adenylyl (adenylate) cyclases, and phospolipases, or PDZ domains.
_b. Ionotropic receptors are ligand-activated ion channels that permit entry of ions when the central pore is open.
סּ active transport סּ ion channels  image - receptor proteins  3D image steroid receptor - Zn finger Џ animation - receptor protein :
There are more than 1200 individual human plasma membrane receptors in more than 20 families. Examples of receptor proteins/receptors include:
a. Guanine nucleotide-binding protein-coupled receptors (GPCRs) (metabotropic).
b. serine threonine kinases (SerThr Kinase) : TGF-β; MAPK cascade; phosphoinositol kinase-related kinase (PIKK) family - mTOR (FRAP1), ATM, ATR, DNA-PK
c. receptor tyrosine kinases (RTKs) : EGFR, Tie receptors, Eph RTKs,
d. cytokine receptors
f. TNF receptors : FAS
Џ beautiful Flash 8 animation - Inner Life of the Cell, which shows membrane adhesion-signaling, and Interpretation: Inner Life of the Cell Џ
• A • adhesion • C • cell membranes • cellular adhesion molecules • cellular signal transduction • centrioles • chemotaxis • chloroplast • cilia & flagella • communication • concentration gradients • cytokine receptors • cytoplasm • cytoskeleton • E • energy transducers • endoplasmic reticulum • endosomes • exosome • F • flagella & cilia • G • Golgi apparatus • GPCRs • H • hormones • I • ion channels • L • lysosome • M • meiosis • microtubules • mitosis • mitochondrion • N • Nitric Oxide • neurotransmission • neuronal interconnections • nuclear membrane • nuclear pore • P • pinocytosis • proteasome • protein degradation • pumps • R • receptor proteins • receptor-mediated endocytosis • S • second messengers • signaling gradients • signal transduction • spindle • structure • T • transport • two-component systems • U • ubiquitin • V • vacuole • vesicle •
. 7 TM receptors & GPCRs . Toll . NPR . Integrins . LDL receptors & LRP . Notch . Patched Plexins . Roundabout . RPTPs . RTKs . Ser/Thr Kinase receptors . TNF receptors . Cytokine 1 receptors . T-cell receptors . Cytokine 2 receptors . Netrin receptors .