6. Cytochalasin B strongly inhibits certain forms of cell motility. In classic e

Question

6. Cytochalasin B strongly inhibits certain forms of cell motility. In classic experiments that defined its mechanism, short lengths of actin microfilaments minus were decorated with myosin heads and then mixed with actin subunits above ed the critical concentration in the presence (+) or absence () oficytochalasin B Assembly of actin microfilaments was assayed by examining samples by electron microscopy. The figure to the right shows results describing the appearance of actin microfilaments formed in the presence and absence of cytochalasin B. The decorated actin microfilaments (gray circles+lines) present before the addition of actin monomers are shown at the top of each set of three. Microfilaments present after increasing times of incubation with actin monomers (red circles) are shown in the next two rows. -cytochalasin 8 end +cytochalasin 8 A. (3pts) Please propose a molecular mechanism for how cytochalasin B affects the dynamics of actin microfilaments that is consistent with the EM data.

Explanation / Answer

Here we can see that actin polymerization occurs highly at positive end and very minute rate of polymerization occurred at negative and of polymerizing actin.

cytochelasin B is an inhibitor of polymerization of actn hence inhibit muscle contraction.

Nucletion core: for high rate of polymerization a particular level of polymerization of actin is required which is known as nucleation core.

The inhibitor cytochalasin B bounce to the fast growing positive and of the fibrous actin and inhibits the polymerization reaction.

The polymerisation of actin have 3 steps:

Nucleation or initiation: it is the starting step of polymerization in which monument 18 molecule pounds to the fibrous actin.

Elongation: the polymerization of enhanes buy high rate of monument actin attachment.

Annealing: it is a kind of steady state in which polymerization of actin also occurs with depolymerization rate.

This inhibitor have beta unsaturated Ester and thiol group which makes it helpful for the interaction with growing actin. This interaction is helpful in the bonding between actin and molecules of nhibitor.

Various bonding and interactions are responsible for the binding of

inhibitor and actin.

When inhibitor binds at the positive and then monomeric actin molecules are not able to bind with the growing Chain and leads to innhibition.

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