lecture 12 and 13/14 Flashcards
Troponin is a ____ binding protein that regulates muscle contraction
Ca2++
Rho, Rac and Ras (like Rab and Ran) are:
GTPase proteins that influence actin assembly
In many eukaryotic cells, actin can typically be found in what main location
Cell cortex
Filament Dynamics of microtubules and actin filaments are regulated by similar activities
Nucleotide binding and hydrolysis on growing end of the filament b) Proteins acting to influence filaments or monomers
Actin filaments are composed of actin monomers and grow much like microtubules, except ___ is carried by monomers
ATP
In cells the concentration of actin is _____, with about half of it being held in monomers through the action of sequestering proteins
very high
The system equilibrium in the cell is poised for very ____ polymerization
rapid
Filament nucleation occurs by ____ ____or formin activity which is locally stimulated/regulated
Arp complex
Filaments are constantly being remodeled by ______ severing and further addition and branching.
(gelsolin)
Much more actin in cells than needed, so the problem is not availability, but how to keep it out of filaments the solution _____ is sequestering (thymosin and profilin) and _____ capping.
monomer filament
: Crawling of cells over surfaces is an actin-dependent process what anchors the cell
the cortex
: Crawling of cells over surfaces is an actin-dependent process what pulls the cell
myosin II contraction at the back end of the cell
: Crawling of cells over surfaces is an actin-dependent process what pushes the cell
the focal contracts that contain intergrin
when the cells Push - are ______&_________ are extended from the cell body; integrins help provide “traction” by adhesion to substrates
Lamellipodia and filopodia
Actin filament nucleation that produces a branch from existing filaments is controlled directly by:
ARP 2/3 complex
How do ARP complex nucleate new filaments
Side binding and generation of a “Y” shaped branched network
Nucleation of new filaments near the leading edge of cell movement by
ARP complex
Nucleation of new filaments in filopodial extensions occurs by activities of formins, adding to the ________ of the filament and pushing the membrane “spike”_____
plus end outward
___ GTPase polarity and signaling proteins that control regulators of the ___ cytoskeleton
Rho actin
For proteins regulated by GTP/GDP binding, it is the case that:
GTP is bound to the protein and converted to GDP + Pi as it acts on another protein
The protein with GDP bound releases GDP and then binds a new molecule of GTP to do another cycle of regulation
Signaling starts on the exterior of the cell through_____ these help set up _____contacts which are locations of actin filament assembly and signal transduction
integrins focal
Myosin I is involved in
vesicle and membrane movement
Myosin II
sliding/contraction in muscles, cytokinesis contractile ring,
trailing end of migrating cells
Myosins move via
ATP hydrolysis
Muscle contraction involves rapid and dynamic control of contacts between ______ filaments and actin filaments in ordered structures called _____
myosin sarcomeres
Thick filaments (myosin filaments) Thin filaments are...
(actin filaments anchored to Z discs
Thick filaments (myosin filaments) Thin filaments are...
(actin filaments anchored to Z discs
Structure of a sarcomere -
___ is consumed by each head as it moves along the actin filament
ATP, myosin
What is/are the signal(s) that allows muscle contraction
Ca++ binding to troponin
motor neuron->______->t-tuble->_________->sarcoplasmic reticulum->__________
signal, action potential, calcium release
Ca++->________->_________
troponin tropomyosin
Cytokinesis: another contractile function of
____and ______ filaments
actin myosin-II
Kinetochores are microtubule interacting
protein complexes built at ___________________
centromeres in chromosomes
The distance between the poles of the mitotic spindle _____ during progression through anaphase
changes
At metaphase of mitosis when all replicated chromosomes are at the metaphase plate:
The chromosomes are under tension from the poles of the spindle via kinetochore microtubules
A specialized protein structure that assembles at the centromeres of chromosomes and binds spindle microtubules during cell division
kinetochores
Cytokinesis of cells occurs by the interaction of ____ ______ with actin to contract and divide the plasma membrane
myosin II proteins
