8SLB

X-ray structure of CorA N-terminal domain in complex with conformation-specific synthetic antibody C12

Summary for 8SLB

• Entry DOI: 10.2210/pdb8slb/pdb
• Descriptor: Cobalt/magnesium transport protein CorA, sAB C12 Heavy Chain, sAB C12 Light Chain, ... (5 entities in total)
• Functional Keywords: ion channel, magnesium channel, regulatory domain, divalent metal cation binding protein, metal transport, membrane protein
• Biological source: Thermotoga maritima MSB8; More
• Total number of polymer chains: 3
• Total formula weight: 83804.51

Authors

Dominik, P.K.,Erramilli, S.K.,Reddy, B.G.,Kossiakoff, A.A. (deposition date: 2023-04-21, release date: 2023-06-07, Last modification date: 2024-10-23)

Primary citation

Erramilli, S.K.,Dominik, P.K.,Deneka, D.,Tokarz, P.,Kim, S.S.,Reddy, B.G.,Skrobek, B.M.,Dalmas, O.,Perozo, E.,Kossiakoff, A.A.
Conformation-specific Synthetic Antibodies Discriminate Multiple Functional States of the Ion Channel CorA.
J.Mol.Biol., 435:168192-168192, 2023

PubMed Abstract: CorA, the primary magnesium ion channel in prokaryotes and archaea, is a prototypical homopentameric ion channel that undergoes ion-dependent conformational transitions. CorA adopts five-fold symmetric non-conductive states in the presence of high concentrations of Mg, and highly asymmetric flexible states in its complete absence. However, the latter were of insufficient resolution to be thoroughly characterized. In order to gain additional insights into the relationship between asymmetry and channel activation, we exploited phage display selection strategies to generate conformation-specific synthetic antibodies (sABs) against CorA in the absence of Mg. Two sABs from these selections, C12 and C18, showed different degrees of Mg-sensitivity. Through structural, biochemical, and biophysical characterization, we found the sABs are both conformation-specific but probe different features of the channel under open-like conditions. C18 is highly specific to the Mg-depleted state of CorA and through negative-stain electron microscopy (ns-EM), we show sAB binding reflects the asymmetric arrangement of CorA protomers in Mg-depleted conditions. We used X-ray crystallography to determine a structure at 2.0 Å resolution of sAB C12 bound to the soluble N-terminal regulatory domain of CorA. The structure shows C12 is a competitive inhibitor of regulatory magnesium binding through its interaction with the divalent cation sensing site. We subsequently exploited this relationship to capture and visualize asymmetric CorA states in different [Mg] using ns-EM. We additionally utilized these sABs to provide insights into the energy landscape that governs the ion-dependent conformational transitions of CorA.

PubMed: 37394032
DOI: 10.1016/j.jmb.2023.168192

Experimental method

X-RAY DIFFRACTION (2.04 Å)