Cell biologyLesson 3 of 5 in the course Cytoskeleton and cell motility

Actin Structure, Dynamics, and Cellular Functions

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

Actin is a highly abundant protein that forms important structures in the cytoskeleton and in muscle. This lesson introduces the two main forms of actin, its molecular structure, and the polarity of actin filaments.

Actin is a family of multifunctional proteins found in essentially all eukaryotic cells. Actin monomers are building blocks for microfilaments, one of the three major components of the cytoskeleton. In muscle cells, actin also forms the thin filaments of the contractile apparatus.

All flashcards

What is the basic structure of a G-actin monomer?
It has two lobes separated by a cleft that contains an ATP- or ADP-binding site.
How is a typical F-actin filament organized?
Two helical strands of actin subunits wind around one another.
What is treadmilling in an actin filament?
Subunits are added at one end and lost at the other while filament length stays roughly constant.
What does cofilin do to actin filaments?
It binds filament subunits and promotes filament severing and disassembly.
What are two roles of nuclear actin?
It contributes to nuclear architecture and processes such as transcription and gene regulation.

Quiz questions

  1. Which actin regulator helps create branches from an existing filament?Answer: The Arp2/3 complex
  2. Which protein caps the minus end of actin filaments?Answer: Tropomodulin
  3. Which description best characterizes a lamellipodium?Answer: A broad protrusion pushed forward by branched actin
  4. In skeletal muscle, what does calcium do to help initiate contraction?Answer: It alters the troponin–tropomyosin arrangement, exposing myosin-binding sites on actin.
  5. How does latrunculin interfere with actin filament assembly?Answer: It binds G-actin and prevents monomers from joining filaments.

Based on the Wikipedia article Actin, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.

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