Actin Filaments That Are Held Together by the Cross-Linking Protein

Multiple Choice

Actin filaments that are held together by the cross-linking protein fimbrin are not contractile. This is probably because …

A) the very weak cross-linking by this protein cannot convert myosin II activity into a coherent contraction.
B) fimbrin arranges the actin filaments in parallel bundles in which all the plus ends point to the same direction.
C) the very tight packing of actin filaments by this small protein excludes myosin II filaments and other large proteins.
D) fimbrin arranges the actin filaments into gel-like networks in which myosin II activity does not produce contraction.
E) fimbrin is a large protein that binds to several actin filaments and resists contraction.