Recombinant Phaseolus vulgaris Luminal-binding protein
Description
Molecular Identity and Function
Recombinant Phaseolus vulgaris BiP is a 70–75 kDa protein identified in proteomic studies of common bean seeds. It binds unfolded proteins via its substrate-binding domain and utilizes ATP hydrolysis to facilitate proper folding . Key functional attributes include:
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Chaperone activity: Prevents protein aggregation under stress conditions .
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ER stress modulation: Acts as a sensor for the unfolded protein response (UPR), regulating stress-signaling pathways .
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Oligomerization: Forms high-molecular-weight (HMW) complexes (15 nm hydrodynamic radius) in vitro, enhancing stability under thermal stress .
Table 1: Key Biochemical Features of Recombinant Phaseolus vulgaris BiP
BiP’s N-terminal ATPase domain and C-terminal substrate-binding domain are evolutionarily conserved. Its interaction with ER-lumenal client proteins is entropy-driven, mediated by hydrophobic residues .
Role in Recombinant Protein Production
BiP overexpression in transgenic plants impacts recombinant protein yields:
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Positive regulation: Enhances secretion of antibodies (e.g., scFv-Fc) by stabilizing nascent polypeptides .
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Negative regulation: At high levels, triggers UPR-mediated ER stress, activating proteasomal degradation pathways .
Key Findings:
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In Arabidopsis seeds, BiP overexpression delayed leaf senescence by suppressing UPR genes (GmNAC1, GmCystP) and lipid peroxidation .
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Recombinant antibody production in seeds upregulated BiP-linked stress genes (e.g., protein disulfide isomerases, calreticulins), indicating ER stress .
Applications in Biotechnology
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Protein folding aid: Co-expressed with heterologous proteins (e.g., antibodies, enzymes) to improve solubility .
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Stress tolerance: Engineered plants with elevated BiP levels show enhanced resilience to drought and pathogens .
Research Challenges
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Solubility issues: Recombinant BiP tends to form insoluble aggregates unless co-expressed with partner chaperones like HSP40 .
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Species-specificity: Phaseolus vulgaris BiP may exhibit divergent client-binding specificity compared to homologs in Arabidopsis or maize .
