Lecture 10 Flashcards
What does arp stand for?
actin-related protein
what does the arp 2/3 complex do? (4)
binds to the side of existing actin filaments
nucleates assembly of new actin filaments
prevents disassembly at the minus end
causes branching
where do actin filaments diassemble in relation to the lamellipidium?
at the rear
how are the actin bundles placed in filopodia?
Parallel actin bundles
how are filopodia extended?
by actin polymerization pushing on the plasma membrane
What do formins do?
- actin-nucleating proteins attached to the plasma membrane
- add actin monomers to the plus end of actin filaments to form filopodia
why don’t filaments slide back?
they are anchored by ineractions with other actin filaments, via cross linking proteins
what do fliopodia do?
play a key role in guiding the migrating cell by probing the new environment and establishing new contacts with the surrounding ECM
what is the mechanism of animal cell migration?
- cell pushes out protrusions at the leading edge of the cell
- protrusions adhere to the surface
- rear of cell is pulled forward
how do protrusions adhere to the surface?
- focal contacts - containing trans-membrane plasma membrane proteins called integrins
- contractile actin bundles (stress fibres) attach to focal contacts
what motor protein is used to pull the rear of the cell forward?
myosin II
where are intermediate filaments found?
in animals - not unicellular organisms, plants, or fungi
what forms the nuclear lamina?
intermediate filaments underlying the nuclear envelope in nucleated animal cells
what are the properties of intermediate filaments?
10nm diameter
do not bind nucleotides (e.g. ATP, GTP)
strong, rope-like, durable
stable (do not grow and shrink rapidly)
some intermediate filaments disassemble during cell division (nuclear lamins, vimentin filaments) and reassemble in telophase - what is this disassembly triggered by?
Phosphorylation
