Organization of Actin Filaments Actin bundles are actin filaments crosslinked into parallel arrays closely packed. The crosslinking proteins are called actin bundling proteins . Fimbrin is an example wihich occurs in actin bundles forming microvilli. Alfa-actinin occurs in the contractile bundles. For example, the actin bundles of the contractile ring that divides cells during cytokinesis.
Actin networks are loosely crosslinked actin filaments.
The filaments are crosslinked in orthogonal arrays in three-dimensional structures. Filamin is an example of a protein crosslinding actin filaments into networks. Such networks underlie the plasma membrane and support the surface of the cell. Protrusions of the Cell Surface Microvilli exist on cells involved in absorption. The major actin-bundling protein in intestinal microvilli is villin.