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Lecture

Notes taken during lecture


Department
Biology
Course Code
BIO120H1
Professor
Jean Jiang Nash

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LECTURE 15 March 8th
Microfilaments cell adhesion
Intermediate filaments independent
Cytoskeletal networks are dynamic especially microtubules, which can lengthen and
shorten
But there are others who are not dynamic, but static
Cell junctions
3 types: anchoring junctions like Velcro; occluding junctions like Ziploc;
Anchoring junctions: mechanically attach cells to cells or the extracellular
matrix
Occluding junctions: seal the contacts between cells
oPrevents material from passing btw cells
Channel forming junctions: allow small molecules to pass from cell to cell
Todays focus is anchoring junctions
ANCHORING JUNCTIONS
Circle is the cell on average, 50 micrometres across
oDot beside it is a protein, a cell adhesion protein
To adhere cell to adjacent cell, to adhere to the matrix
Cell adhesion proteins are clustered into groups, which increase strength of
interaction between cell
oMany stronger than one
oVelcro effect:
oPulling on whole network, not just hydrophobic interaction
Affinity: the binding strength between two molecules via a single binding site
Avidity: the TOTAL binding strength between two molecules or complexes,
involving multiple binding sites
oNote the multiple binding sites
Avidity greater than sum of parts because of the Velcro effect
oInteraction represented by red line
oFrequency of binding or releasing built into affinity concept
oAs for avidity two proteins linked together at top two binding sites
With same rate of loss and binding instead of floating away, held
close to protein partner likely to bind to its protein partner
Note that one arrow is darker
One is likely to break, the other is going to form rightaway
Must have both bonds broken together to totally separate
If one Velcro hook disengaged, still majority engaged
Cytoskeletal attachments
Adherens cell-cell
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