Nucleotide State Regulates Asymmetric Substrate-Binding Protein Docking in a Type II ABC Importer
- 1Northwestern University
Abstract
Type II ABC importers rely on substrate-binding proteins (SBP) to capture nutrients and deliver them to membrane-embedded transporters, but how ATP binding and hydrolysis regulate their interactions remains poorly understood. To address these questions, we determined structures of the Type II small-substrate molybdate importer MolBC-A from H. influenzae in distinct nucleotide-bound states, complemented by molecular dynamics (MD) simulations and functional assays. In a nucleotide-free state, the MolA-MolBC interface is remodeled into a more open conformation, whereas ATP and AMP-PNP binding induce asymmetric conformational changes that preserve the MolA Lobe I interface and disrupt contacts with MolA Lobe II, revealing a previously unresolved partially-docked state. In the ADP-bound state, MolA exhibits the greatest conformational heterogeneity with reduced stable engagement that extends across both lobes. Together these findings define a nucleotide-dependent cycle of asymmetric MolA remodeling and reveal distinct contributions of the two SBP lobes in coupling transporter nucleotide state to SBP engagement.
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BibTeX
@misc{karagiaridi2026nucleotide,
title = {{Nucleotide State Regulates Asymmetric Substrate-Binding Protein Docking in a Type II ABC Importer}},
author = {A. Karagiaridi and R. Mendoza Uriarte and M. Chen and B. Roux and H. W. Pinkett},
howpublished = {bioRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.15.759412},
url = {https://www.biorxiv.org/content/10.64898/2026.10.15.759412v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Nucleotide State Regulates Asymmetric Substrate-Binding Protein Docking in a Type II ABC Importer
AU - A. Karagiaridi
AU - R. Mendoza Uriarte
AU - M. Chen
AU - B. Roux
AU - H. W. Pinkett
PY - 2026
DA - 2026/10/15
PB - bioRxiv
DO - 10.64898/2026.10.15.759412
UR - https://www.biorxiv.org/content/10.64898/2026.10.15.759412v1
AB - Type II ABC importers rely on substrate-binding proteins (SBP) to capture nutrients and deliver them to membrane-embedded transporters, but how ATP binding and hydrolysis regulate their interactions remains poorly understood. To address these questions, we determined structures of the Type II small-substrate molybdate importer MolBC-A from H. influenzae in distinct nucleotide-bound states, complemented by molecular dynamics (MD) simulations and functional assays. In a nucleotide-free state, the MolA-MolBC interface is remodeled into a more open conformation, whereas ATP and AMP-PNP binding induce asymmetric conformational changes that preserve the MolA Lobe I interface and disrupt contacts with MolA Lobe II, revealing a previously unresolved partially-docked state. In the ADP-bound state, MolA exhibits the greatest conformational heterogeneity with reduced stable engagement that extends across both lobes. Together these findings define a nucleotide-dependent cycle of asymmetric MolA remodeling and reveal distinct contributions of the two SBP lobes in coupling transporter nucleotide state to SBP engagement.
ER -