Molecular chaperones and protein folding in plants

Abstract

Protein folding in vivo is mediated by an array of proteins that act either as 'foldases' or 'molecular chaperones'. Foldases include protein disulfide isomerase and peptidyl prolyl isomerase, which catalyze the rearrangement of disulfide bonds or isomerization of peptide bonds around Pro residues, respectively. Molecular chaperones are a diverse group of proteins, but they share the property that they bind substrate proteins that are in unstable, non-native structural states. The best understood chaperone systems are HSP70/DnaK and HSP60/GroE, but considerable data support a chaperone role for other proteins, including HSP100, HSP90, small HSPs and calnexin. Recent research indicates that many, if not all, cellular proteins interact with chaperones and/or foldases during their lifetime in the cell. Different chaperone and foldase systems are required for synthesis, targeting, maturation and degradation of proteins in all cellular compartments. Thus, these diverse proteins affect an exceptionally broad array of cellular processes required for both normal cell function and survival of stress conditions. This review summarizes our current understanding of how these proteins function in plants, with a major focus on those systems where the most detailed mechanistic data are available, or where features of the chaperone/foldase system or substrate proteins are unique to plants.

Modified Clp Protease Complex in the ClpP3 Null Mutant and Consequences for Chloroplast Development and Function in Arabidopsis

“…The up-regulated proteins include the chloroplast chaperones CPN60a,b (Fig. 10), CPN10,20, cpHSP70-1,2, and cpHSP90, which play crucial roles in protein folding and maturation (Boston et al, 1996;Wandinger et al, 2008). ClpB3, the chloroplast homolog of the bacterial ClpB protein (Myouga et al, 2006), was 5-fold up-regulated.…”

Molecular chaperone genes in the sugarcane expressed sequence database (SUCEST)

“…The Hsp100 family is involved in protein disaggregation, acting together with the Hsp70 system (Schirmer et al, 1996). Little is known about the function of the Small Hsp (sHsp) set of proteins, a family which is not highly conserved and whose cytoplasmic forms represent 1% of the total proteins present in a thermally stressed cell (Jakob and Buchner, 1994;Boston et al, 1996). Peptidyl-prolyl cis, trans isomerase (PPIase) catalyses the cis, trans isomerization of Proline peptide bonds in proteins.…”

Relevant Elements of a Maize γ-Zein Domain Involved in Protein Body Biogenesis

“…Thus, although ␥-and ␤-zeins accumulated in PBs in transgenic Arabidopsis and tobacco plants (10,11), ␣-and ␦-zeins only accumulated if they were coexpressed with ␥-and ␤-zeins, respectively, in transgenic tobacco, indicating that ␥-zein and ␤-zein have a stabilizing effect on other zeins (12,13). Trans-acting interactions between prolamins and ER-residing chaperones, such as BiP, also play a role in prolamin retention by facilitating its folding and assembly (5,14,15). In rice, the localized targeting of prolamin mRNAs to distinct ER subdomains also facilitates the assembly and retention of these proteins (16,17).…”