# Actin arginylation alters myosin engagement and F-actin patterning despite structural conservation

## TL;DR

Arginylation of actin changes how it interacts with myosin and organizes into structures in cells, even though its structure remains mostly the same.

## Contribution

The study reveals that arginylated actin alters myosin-II interactions and F-actin organization despite structural conservation.

## Key findings

- Arginylated β-actin filaments have nearly identical structures to non-arginylated actin.
- Arginylation disrupts myosin-II interactions and affects cytokinesis in cells.
- R-actin alters actin filament organization in vivo, impacting subcellular structures.

## Abstract

Actin is vital for cell functions and is regulated by posttranslational modifications like arginylation. The structure of arginylated β-actin (R-β-actin) is nearly identical to non-modified actin. However, arginylation alters myosin-II interactions and impacts actin filament organization and cytokinesis in cells.

Actin is a conserved protein with crucial roles in cell polarity, division, and muscle contraction. Its function is regulated in part by posttranslational modifications, one of which is N-terminal arginylation. What is the structure of arginylated-β-actin (R-β-actin), and how does it regulate F-actin function? Here we report the 3.6 Å structures of ADP-R-β-actin filaments, which are nearly identical to that of non-arginylated F-actin. In vitro assays reveal that the interaction between myosin-II and actin is altered upon actin arginylation, characterized by frequent detachment of R-actin filaments from myosin-II. In vivo, replacement of the only actin gene in Schizosaccharomyces pombe with a synthetic gene encoding R-Sp-actin reduces Arp2/3-based actin patches while thickening formin-induced actin cables. Consistent with defective interactions between myosin-II and R-actin filaments, assembly and constriction of the cytokinetic actomyosin ring are perturbed in R-Sp-actin cells. Thus, despite structural similarity of arginylated and non-arginylated actin filaments, actin arginylation affects F-actin assortment into distinct subcellular structures and its interaction with myosin-II.