FTSHI4 Antibody

Definition and Target Protein

FTSHI4 (Filamentous temperature-sensitive H protease 4) is a member of the FtsHi protein family, which lacks Zn²⁺-binding motifs but shares homology with FtsH proteases. It is localized in chloroplast thylakoid membranes and is indispensable for embryogenesis due to its role in photosystem II (PSII) assembly .

Antigen Details:

• Immunogen: Synthetic oligopeptide sequence SETSGRVFARKSDY, corresponding to residues within the FTSHI4 protein .

• Host Species: Rabbit.

• Specificity: Recognizes FTSHI4 in Arabidopsis and cross-reacts with homologs in Brassica napus, Glycine max, Oryza sativa, and other plant species .

Production

• Immunization: Rabbits were immunized with the synthetic peptide conjugated to a carrier protein .

• Purification: Affinity-purified using the immunogen peptide .

Validation

• Western Blot: Detects endogenous FTSHI4 (~105 kDa) in wild-type Arabidopsis but not in ftshi4 mutants .

• Localization: Confirmed via immunocytochemistry to associate with thylakoid membranes in chloroplasts .

Key Validation Data

Functional Studies

• Embryogenesis: FTSHI4 is essential for embryo development beyond the globular stage. Mutants exhibit arrested embryos with defective plastids .

• Chloroplast Development: Required for thylakoid membrane formation and PSII protein accumulation (e.g., D1, D2, PsbO) .

Mechanistic Insights

• Protein Complexes: FTSHI4 interacts with other FtsHi proteins (FtsHi1, FtsHi2, FtsHi5) to form complexes critical for chloroplast biogenesis .

• Topology: Despite earlier assumptions, FTSHI4’s ATPase domain is not stromal but membrane-embedded, influencing its role in protein import .

Key Research Findings

1. Embryo Lethality: Homozygous ftshi4 mutants fail to develop beyond the heart-shaped embryo stage due to impaired plastid differentiation .

2. PSII Defects: RNAi-mediated knockdown of FTSHI4 reduces D2 and PsbO protein levels, disrupting PSII function .

3. Conservation: FTSHI4 homologs are present across angiosperms, suggesting a conserved role in chloroplast development .

Technical Considerations

• Storage: Lyophilized antibodies should be stored at -20°C; avoid repeated freeze-thaw cycles .

• Controls: Always include wild-type and ftshi4 mutant samples to confirm specificity .