Related Experiment Video
Updated: Dec 17, 2025
Targeted Next-generation Sequencing and Bioinformatics Pipeline to Evaluate Genetic Determinants of Constitutional Disease
Published on: April 4, 2018
Computational analysis identifies druggable mutations in human rBAT mediated Cystinuria
Bharati Pandey1, Murali Aarthy2, Mahima Sharma1
1Radiation Biology & Health Sciences Division, Bhabha Atomic Research Centre, Mumbai, India.
Abstract:
Culex quinquefasciatus Cqm1 protein acts as the receptor for Lysinibacillus sphaericus mosquito-larvicidal binary (BinAB) toxin that is used worldwide for mosquito control. We found amino acid transporter protein, rBAT, as phylogenetically closest Cqm1 homolog in humans. The present study reveals large evolutionary distance between Cqm1 and rBAT, and rBAT ectodomain lacks the sequence motif which serves as binding-site for the BinAB toxin. Thus, BinAB toxin can be expected to remain safe for humans. rBAT (heavy subunit; SLC3A1) and catalytic b0,+AT (light subunit; SLC7A9), linked by single disulfide bond, mediate renal reabsorption of cystine and dibasic amino acids in Na+ independent manner. Mutations in rBAT cause type I Cystinuria disease which shows global prevalence, and rBAT can be thought as an important pharmacological target. However, 3D structures of rBAT and b0,+AT, the two components of b0,+ heteromeric amino acid transporter systems, are not available. We constructed a reliable homology model of rBAT using Cqm1 coordinates and that of transmembrane b0,+AT subunit using LAT1 coordinates. Mapping of pathogenic mutations onto rBAT ectodomain revealed their scattered distribution throughout the rBAT protein. Further, our computational simulations-based scoring of several known deleterious mutations of rBAT revealed that mutations those do not compromise the protein fold and stability, are localized on the same face of the molecule. These residues are expected to interact with the b0,+AT transporter. The present study thus identifies druggable sites on rBAT that could be targeted for the treatment of type I Cystinuria.Communicated by Ramaswamy H. Sarma.
Insights
The mosquito toxin BinAB is safe for humans as it does not bind to the human homolog rBAT. This study models rBAT, identifying potential drug targets for treating cystinuria.
Area of Science:
- Biochemistry
- Structural Biology
- Pharmacology
Background:
- The mosquito Cqm1 protein binds the Lysinibacillus sphaericus mosquito-larvicidal binary (BinAB) toxin, used for mosquito control.
- The human homolog of Cqm1 is the amino acid transporter protein rBAT (heavy subunit; SLC3A1), which forms a heteromeric system with b0,+AT (light subunit; SLC7A9).
- Mutations in rBAT cause type I Cystinuria, a prevalent disease, making rBAT a potential pharmacological target, yet its 3D structure is unknown.
Purpose of the Study:
- To determine if the BinAB toxin poses a safety risk to humans by assessing its binding to human rBAT.
- To develop homology models for rBAT and the transmembrane b0,+AT subunit.
- To identify potential druggable sites on rBAT for treating type I Cystinuria.
Main Methods:
- Comparative analysis of Cqm1 and human rBAT sequences to assess evolutionary distance and potential toxin binding.
- Homology modeling of the rBAT ectodomain using Cqm1 coordinates and the transmembrane b0,+AT subunit using LAT1 coordinates.
- Mapping and computational simulation-based scoring of pathogenic mutations on the rBAT model.
Main Results:
- A significant evolutionary distance exists between Cqm1 and rBAT, and rBAT lacks the toxin-binding motif, indicating BinAB toxin safety for humans.
- Reliable 3D homology models of rBAT and b0,+AT were constructed.
- Pathogenic mutations on rBAT, not compromising protein fold, cluster on a face likely interacting with b0,+AT, suggesting druggable sites.
Conclusions:
- The BinAB toxin is unlikely to bind to human rBAT, ensuring its safety for human use.
- The developed homology models provide a structural basis for understanding rBAT function and disease mechanisms.
- Specific druggable sites on rBAT have been identified for potential therapeutic interventions in type I Cystinuria.
