Homologous plant and bacterial proteins chaperone oligomeric protein assembly

Abstract

An abundant chloroplast protein is implicated in the assembly of the oligomeric enzyme ribulose bisphosphate carboxylase-oxygenase, which catalyses photosynthetic CO2-fixation in higher plants. The product of the Escherichia coli groEL gene is essential for cell viability and is required for the assembly of bacteriophage capsids. Sequencing of the groEL gene and the complementary cDNA encoding the chloroplast protein has revealed that these proteins are evolutionary homologues which we term 'chaperonins'. Chaperonins comprise a class of molecular chaperones that are found in chloroplasts, mitochondria and prokaryotes. Assisted post-translational assembly of oligomeric protein structures is emerging as a general cellular phenomenon.

Molecular chaperones are present in the thylakoid lumen of pea chloroplasts

“…2b). This is in accordance with the calculated isoelectric points of the cpn60 a and fl isoforms from pea chloroplasts of 4.6 and 5.1, respectively [11,12]. In order to clearly demonstrate a possible difference between the cpn60 isoforms, lumenal and stromal proteins were mixed prior to electrophoresis.…”

“…The cpn60/cpnl0 system operating in the chloroplast stroma [9][10][11][12] is unique in comparison to other organelles or prokaryotes [13][14][15]. Stromal cpn60 exists in two isoforms ~ andfl in the chloroplasts [11,12] and its co-chaperonin 10 is comprised of two distinct cpnl0 like domains, fused in tandem to give a binary co-chaperonin structure [9,16].…”

“…Stromal cpn60 exists in two isoforms ~ andfl in the chloroplasts [11,12] and its co-chaperonin 10 is comprised of two distinct cpnl0 like domains, fused in tandem to give a binary co-chaperonin structure [9,16]. The reasons for the presence of the special composition of the stromal cpn60/cpnl0 is unknown in the moment, because it has been demonstrated that *Corresponding author.…”

Firefly luciferase mutants as sensors of proteome stress

“…Chaperones, transiently and non-covalently, shield the exposed hydrophobic surfaces on their substrate clients and prevent their non-specific interactions with other molecules. These proteins, in some cases, can also facilitate the post-translational assembly of polypeptides into oligomeric structures as in the assembly of the functional enzyme Ribulose-1,5-bisphosphate carboxylase oxygenase (Rubisco) (Hemmingsen et al, 1988;Liu et al, 2010;Saschenbrecker et al, 2007). Many of the chaperones promote de novo folding by iterative cycles of substrate binding and release driven by ATP hydrolysis and may require co-factors or co-chaperones.…”

The Tetrahymena chaperonin subunit CCTη gene is coexpressed with CCTγ gene during cilia biogenesis and cell sexual reproduction

“…One of the partlcularly well studied families of molecular chaperones is the cllaperonins [2,3]. Members of this protein family were first identified in eubacteria (GroEL in Escherichia coli) [4] and in o:rtain organelles of eukaryotic cells, such as mitochondria (I-Isp60 in mitochondrial matrix) [5] and chloroplasts (Rubisc,)-subunit-binding protein, RBP) [6]. These proteins assemble irito large oligomeric complexes of 60 kDa subunits that are usually arranged as two stacked heptameric rings with a central cavity (for review [2,3]).…”