LIFE 210 Lecture Notes - Nebulin, Spindle Apparatus, Endoplasmic Reticulum
Document Summary
Muscle contraction depends on the atp-driven sliding of highly organized arrays of actin filaments against myosin ii filaments. A muscle fiber is a huge single cell formed during development by the fusion of many separate myoblasts. Typically 50 m in diameter and up to several centimeters long. A myofibril consists of a long repeated chain of sarcomeres. Partly overlapping array of parallel thin (actin) and thick (myo ii) filaments. Electron micrograph of an insect flight muscle viewed in cross section. Region of overlap between thin and thick filaments. The ~300 myosin heads in a thick filament are not coordinated, therefore low processivity is critical. Actin filament plus end binds to the z disc, which is built by capz and -actinin. Nebulin is a large protein with an actin-binding repeat. Tropomodulin positions the thick filament midway between the z discs. The force generated during contraction depends on the degree of overlap of the thick and thin filaments.
