6. You have two different myosin molecules (A and B) in hand, and you would like
ID: 253048 • Letter: 6
Question
6. You have two different myosin molecules (A and B) in hand, and you would like to get some idea about whether they are likely to function as a contractile force producer or an organelle transportation motion. You designed an experiment to measure the fraction of time (as numbers given in the table below) when each myosin stays in a certain nucleotide-bound state during the ATPase cycle in the presence of actin filaments. Estimate the duty ratio for each myosin based on this data (2 pts each) ATP-bound 0.52 0.30 nucleotide free Myosin A Myosin B ATP-Pi-bound ADP-bound 0.33 0.13 0.08 0.37 0.07 0.20 What function are you more likely to hypothesize for each myosin based on this estimation? (2 pts)Explanation / Answer
Duty Ratio: fraction of time that a myosin head is bound to the filament. How long ADP molecules binds in myosin directly related to myosin head is bound to the filament.
Myosin A = 0.08/0.52 = 0.13
Myosin B = 0.37/0.30 = 1.23
The motor proteins walk continuously, the duty ratio has to be greater than 50% one of the two heads has to be bound at all the times.
So, Myosin B is a motor protein or myosin V.
Myosin A or Myosin 2 have short duty ratios in skletal system.
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