16C Assignment Flashcards
What is the most conserved region of myosin heavy chain relative to other members of the myosin protein family? (Why do you think this domain has been conserved…)
Motor Domain
In this experimental setup myosin grabs an actin filament like a chin-up bar. This leads to the short, dense, and steady regions seen in (B) with an ~10 nm displacement and reveals single myosin /actin binding events. These events were a challenge to record, but a clever trick allowed the research group to achieve an extended binding duration and made imaging more robust. What did they do? (and why did it work…)
added extra ATP
added an irreversible chemical cross-linker
added only very limited ATP
added an excess of ADP
depleted ADP
added only very limited ATP
Drives the allosteric (protein) conformation change resulting in myosin release from actin.
ATP
ADP
Pi
AMP
GTP
ATP
Energy from the hydrolysis of this molecule is captured in a spring-like allosteric change in myosin.
ATP
ADP
Pi
AMP
GTP
ATP
Released from cocked myosin upon weakly binding to a new site on actin.
ATP
ADP
Pi
AMP
GTP
Pi
Released during the myosin power stroke.
ATP
ADP
Pi
AMP
GTP
ADP
Which area is characterized by abundant myosin?
A. Z disc
B. dark band
C. light band
B. dark band
Which area is characterized by abundant actin
A. Z disc
B. dark band
C. light band
C. light band
Which move closer together when Ca2+ is released into the structure shown?
A. Z disc
B. dark band
C. light band
A. Z disc
In the experimental setup shown, purified phalloidin-labeled actin glides around on a bed of glass-immobilized purified myosin. (the associated movie is worth watching!). A student decides to use this setup to test ideas about calcium concentrations and manipulates the system by adding increasing amounts of the potent calcium chelator inactivator (also known as a chelator) EGTA. What happens?
Actin slows down then speeds up.
Actin speeds up, but the slows down.
Actin speeds up with increasing EGTA
Actin slows down with increasing EGTA
Very little change
Very little change
In addition to muscle activity, myosin is also associated with:
Movement of vesicles
Adjusting tension and cell shape by exerting force between the PM and cortical actin
Cell locomotion
Constricting the contractile belt during cytokinesis
All of the answers
All of the answers
