# Unveiling the Mechanistic Impact of Mutations F2004C/V in the ROS1 Kinase Domain

## TL;DR

This study explores how specific mutations in the ROS1 kinase domain affect cancer drug responses by analyzing structural changes in the protein.

## Contribution

The paper introduces a structural model of the inactive conformation of the ROS1 kinase domain and explains how F2004C/V mutations influence inhibitor responses.

## Key findings

- F2004C/V mutations do not affect the active conformation of ROS1 kinase.
- These mutations stabilize a hydrophobic cluster in the inactive conformation.
- The mutations explain differential responses to type I and II inhibitors.

## Abstract

The emergence of fusion proteins that express the ROS1
kinase domain
has become a promising target in non-small-cell lung cancer (NSCLC).
Although earlier kinase inhibitors effectively managed ROS1-positive
tumors, the rise of point mutations, particularly those beyond the
binding pocket, has challenged the inhibitor efficacy. Notably, mutations
at residue F2004, which cause cysteine or valine substitution, exhibit
intriguing response profiles to the inhibitors. These mutations respond
to small molecules that target the active conformation of the kinase
(type I) but resist inhibitors that explore the inactive conformation
(type II). Our study generates a ROS1 kinase model and uses molecular
dynamics simulations to discern structural differentiators of the
inactive conformation. A hydrophobic cluster within the active site,
involving DFG residue F2103, demarcates the active conformation. We
unveil insights from F2004C/V mutations in the ROS1 kinase domain
from both the active and inactive states. Notably, the mutations do
not perturb the active conformation, resembling wild-type (WT) ROS1.
However, in the inactive conformation, the mutations disrupt the flexibility
of DFG residue F2103, stabilizing the hydrophobic cluster. Our results
provide a model for the inactive conformation of the elusive ROS1
kinase domain, offering pivotal insights into potential differences
from the active conformation. Furthermore, our study of F2004C/V mutants
proposes a plausible mechanism underlying the type I or II inhibitor
response.