Crystal structure of monomeric actin in the ATP state. Structural basis of nucleotide-dependent actin dynamics

J Biol Chem. 2003 Sep 5;278(36):34172-80. doi: 10.1074/jbc.M303689200. Epub 2003 Jun 17.


A nucleotide-dependent conformational change regulates actin filament dynamics. Yet, the structural basis of this mechanism remains controversial. The x-ray crystal structure of tetramethylrhodamine-5-maleimide-actin with bound AMPPNP, a non-hydrolyzable ATP analog, was determined to 1.85-A resolution. A comparison of this structure to that of tetramethylrhodamine-5-maleimide-actin with bound ADP, determined previously under similar conditions, reveals how the release of the nucleotide gamma-phosphate sets in motion a sequence of events leading to a conformational change in subdomain 2. The side chain of Ser-14 in the catalytic site rotates upon Pi release, triggering the rearrangement of the loop containing the methylated His-73, referred to as the sensor loop. This in turn causes a transition in the DNase I-binding loop in subdomain 2 from a disordered loop in ATP-actin to an ordered alpha-helix in ADP-actin. Despite this conformational change, the nucleotide cleft remains closed in ADP-actin, similar to ATP-actin. An analysis of the existing structures of members of the actin superfamily suggests that the cleft is open in the nucleotide-free state.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Actins / chemistry*
  • Adenosine Triphosphate / chemistry
  • Adenosine Triphosphate / metabolism*
  • Adenylyl Imidodiphosphate / chemistry
  • Catalytic Domain
  • Crystallography, X-Ray
  • Deoxyribonuclease I / chemistry
  • Deoxyribonucleases / chemistry
  • Fluorescent Dyes / pharmacology
  • Histidine / chemistry
  • Models, Molecular
  • Nucleotides / chemistry
  • Phosphates / chemistry
  • Protein Binding
  • Protein Conformation
  • Protein Structure, Tertiary
  • Rhodamines / pharmacology
  • Serine / chemistry


  • Actins
  • Fluorescent Dyes
  • Nucleotides
  • Phosphates
  • Rhodamines
  • Adenylyl Imidodiphosphate
  • Serine
  • Histidine
  • tetramethylrhodamine
  • Adenosine Triphosphate
  • Deoxyribonucleases
  • Deoxyribonuclease I

Associated data

  • PDB/1NWK