Structures and mechanisms of actin ATP hydrolysis

Yusuke Kanematsu, Akihiro Narita, Toshiro Oda, Ryotaro Koike, Motonori Ota, Yu Takano, Kei Moritsugu, Ikuko Fujiwara, Kotaro Tanaka, Hideyuki Komatsu, Takayuki Nagae, Nobuhisa Watanabe, Mitsusada Iwasa, Yuichiro Maéda, Shuichi Takeda

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)

Abstract

The major cytoskeleton protein actin undergoes cyclic transitions between the monomeric G-form and the filamentous F-form, which drive organelle transport and cell motility. This mechanical work is driven by the ATPase activity at the catalytic site in the F-form. For deeper understanding of the actin cellular functions, the reaction mechanism must be elucidated. Here, we show that a single actin molecule is trapped in the F-form by fragmin domain-1 binding and present their crystal structures in the ATP analog-, ADP-Pi-, and ADP-bound forms, at 1.15-Å resolutions. The G-to-F conformational transition shifts the side chains of Gln137 and His161, which relocate four water molecules including W1 (attacking water) and W2 (helping water) to facilitate the hydrolysis. By applying quantum mechanics/molecular mechanics calculations to the structures, we have revealed a consistent and comprehensive reaction path of ATP hydrolysis by the F-form actin. The reaction path consists of four steps: 1) W1 and W2 rotations; 2) PG–O3B bond cleavage; 3) four concomitant events: W1–PO32 formation, OH2 and proton cleavage, nucleophilic attack by the OH2 against PG, and the abstracted proton transfer; and 4) proton relocation that stabilizes the ADP-Pi–bound F-form actin. The mechanism explains the slow rate of ATP hydrolysis by actin and the irreversibility of the hydrolysis reaction. While the catalytic strategy of actin ATP hydrolysis is essentially the same as those of motor proteins like myosin, the process after the hydrolysis is distinct and discussed in terms of Pi release, F-form destabilization, and global conformational changes.

Original languageEnglish
Article numbere2122641119
JournalProceedings of the National Academy of Sciences of the United States of America
Volume119
Issue number43
DOIs
Publication statusPublished - Oct 25 2022

Keywords

  • actin
  • ATP hydrolysis
  • protein crystallography
  • QM/MM simulation

ASJC Scopus subject areas

  • General

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