BIOC 212 Lecture Notes - Lecture 30: Fibrinogen, Phenylalanine, Hemidesmosome
29 May 2018
School
Department
Course
Professor
Cell Junctions & Cell Adhesion X
!
The Mammalian Integrin Receptor Family
• Heterodimeric transmembrane glycoprotein receptors (α and β subunit)
o 18 alpha and 8 beta subunits form 24 integrins
• Theoretically, if each alpha subunit to interact with any beta, would have
8 x 18 integrin heterodimers possible
• However, in humans only find 24 integrin heterodimer (always made of
one alpha & one beta subunit)
o Alpha subunits able to pair with various beta subunits
• Evolutionary old RGD receptors
o Interact with RGD sequence in target protein
o RGD is one letter amino acid code
• Collagen receptors
• Laminin receptors
o Laminin are major proteins in BM membrane
o Several integrins interact with these receptors
• These three where cell-ECM interactions
• Leukocyte-specific receptor
o Specific to WBCs, recognize Ig-like CAMs
o Cell-cell interaction
• Some of these subunits are further alternatively spliced, giving to greater variety (*)
Integrin Heterodimers
• TM proteins with short cytosolic tail (C-terminus)
• TM proteins Type I
o Each subunit crosses the membrane once
o Protein with carboxy-terminus inside the cell and N-terminal outside the cell
• Most of each polypeptide is in the extracellular space (>1600 aa)
o For both alpha & beta subunits
o Cytoplasmic domain is relatively short for most integrins (20-50 aa)
• Large head domain of each subunit come together to form matrix protein binding
site
o Certain domains help forming spacer between PM and head group
o Help binding matrix proteins better
• If head domain was very close to PM, large ECM proteins would not be
able to bind as efficiently
• Ligand specificity relies on both subunits
o Integrins serve as TM mechanical links from the ECM to the cytoskeleton
inside cells
Document Summary
The mammalian integrin receptor family: heterodimeric transmembrane glycoprotein receptors ( and subunit, 18 alpha and 8 beta subunits form 24 integrins, theoretically, if each alpha subunit to interact with any beta, would have. 8 x 18 integrin heterodimers possible: however, in humans only find 24 integrin heterodimer (always made of one alpha & one beta subunit, alpha subunits able to pair with various beta subunits, evolutionary old rgd receptors. If head domain was very close to pm, large ecm proteins would not be able to bind as efficiently: ligand specificity relies on both subunits. Integrins serve as tm mechanical links from the ecm to the cytoskeleton inside cells: all integrins (except alpha6beta4) are connected to the actin based microfilaments system, a6b4 is in hemidesmosomes (if, regulation & modulation. Integrin-binding sequences (on ecm proteins: number of ecm protein that all have rgd sequence, fibronectin, collagen, fibrinogen, etc, arginine, glycine, aspartic acid.
