– Chaperone protein required for seedling and chloroplast development under heat stress, probably by maintaining plastid-encoded RNA polymerase (PEP)-dependent transcription. HSP21, chloroplastic Protein, Arabidopsis thaliana, Recombinant (His & Myc) is expressed in E. coli expression system with N-10xHis and C-Myc tag. The predicted molecular weight is 28.4 kDa and the accession number is P31170.