Molecular characterization of Oryza sativa 16·9 kDa heat shock protein

Abstract

A rice class I low-molecular-mass heat shock protein (LMM HSP) Oshsp 16.9 was overexpressed in Escherichia coli. Oligomerized complexes of Oshsp16.9 were harvested and electron microscopic observations of purified complexes revealed globular structures of 10-20 nm in diameter (with majority of 15-18 nm) and calculated to comprise approx. 12 monomers per complex. In comparison, complexes from native rice class I LMM HSPs were observed as larger ellipsoid- or globular-like random aggregated hetero-oligomers. To characterize the biochemical functions of the hydrophobic N-terminal region of Oshsp16.9, a truncation in the N-terminal region was constructed and introduced into E. coli. Results showed that the N-terminal truncated Oshsp16.9 mutant was capable of forming complexes similar to the full-length Oshsp16.9; however, the deletion protein failed to confer in vitro protein thermostability under elevated temperatures. Protein assays from in vivo treatments at higher temperatures exhibited that non-specific interactions of E. coli cellular proteins only occurred with full-length Oshsp16.9 complexes but not with the mutant complex. In vitro immunoprecipitation of cellular proteins from E. coli overexpressing full-length Oshsp16.9 showed that interactions between plant LMM HSP and E. coli cellular proteins are temperature-dependent. Taken together, the hydrophobic N-terminal region of rice class I LMM HSP is critical in the ability of the protein to interact/bind with its potential substrates.

Proteome Analysis of Hordein-Null Barley Lines Reveals Storage Protein Synthesis and Compensation Mechanisms

“…Increased abundance of HSPs indicates their potential role in processing the elevated levels of B- and C-hordeins, which together represent >95% of total prolamin. Increased abundance of HSPs was reported earlier in rice, wheat, and a high-lysine maize mutant, where the synthesis of storage proteins is common.…”

Extrapolating the effect of non-synonymous SNP in bread wheat HSP16.9B gene: a molecular modelling and dynamics study

“…It was reported that β2 strand was involved in structure dimerisation of HSP16.5 and HSP 16.9. The β7 strand was found to play crucial role in the dimer formation in the human sHSP proteins (Young et al, 1999) and presence of conserved arginine residue significantly contributes to dimerisation and found to be associated with human pathologies (Carugo and Pongor, 2001). The solved crystal structure of HSP16.5 and HSP16.9 from M. jannaschii and wheat respectively, revealed that swapping of β6 strand leads to protein dimer formation and oligomerisation (van Montfort et al, 2001b).…”