CRS2B Antibody

Definition and Molecular Identity

CRS2B (Chloroplastic RNA Splicing Factor 2-B) is a nucleus-encoded protein critical for the splicing of group IIB introns in chloroplasts. It belongs to the peptidyl-tRNA hydrolase (PTH) family but lacks enzymatic PTH activity due to non-conservative substitutions in key catalytic residues . Instead, CRS2B facilitates RNA splicing by forming ribonucleoprotein complexes with intron RNA .

Key identifiers:

• UniProt ID: Q9LF14

• Gene: At5g16140 (Arabidopsis thaliana)

Structure and Functional Domains

CRS2B shares structural homology with bacterial PTH proteins but diverges in critical regions required for enzymatic activity. Key features include:

CRS2B interacts directly with group IIB introns, stabilizing RNA structures essential for splicing . Its RNA-binding activity is salt-stable and nuclease-sensitive, confirming its role in RNA processing .

Mechanism of Action

CRS2B facilitates the splicing of chloroplast group IIB introns through:

1. RNA Binding: Co-sediments with intron RNA (e.g., petB and ndhB introns) but not crs2-independent introns like atpF .

2. Complex Assembly: Forms a ribonucleoprotein complex critical for splicing fidelity .

3. Cooperative Function: Works alongside other splicing factors (e.g., CRS2 in maize) to enable intron excision .

Key experimental findings:

• CRS2B-deficient mutants show impaired splicing of chloroplast group IIB introns, leading to defective chloroplast biogenesis .

• CRS2B’s RNA-binding activity is abolished by micrococcal nuclease treatment, confirming its dependence on RNA .

Applications and Research Tools

CRS2B antibodies are widely used to study chloroplast RNA splicing mechanisms. Commercial antibodies (e.g., Cat. No. BT1227891) are validated for:

• Immunoblotting: Detects ~70 kDa CRS2B protein in chloroplast stroma.

• Complex Analysis: Identifies CRS2B-containing ribonucleoprotein complexes via sucrose gradient sedimentation .

Comparative Analysis:

Research Implications

CRS2B antibodies have advanced understanding of:

• Chloroplast gene expression and photosynthesis .

• Evolutionary repurposing of PTH-like proteins in organellar RNA processing .

• Mechanisms of ribonucleoprotein assembly in plants .

Unresolved Questions

1. Does CRS2B interact with additional cofactors in Arabidopsis?

2. How does CRS2B achieve intron specificity despite lacking sequence-specific RNA-binding domains?

3. Structural basis of CRS2B-RNA interactions remains uncharacterized.