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Query: UNIPROT:P06889 (Mol)
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Synechocystis PCC 6803 cells could be induced to synthesize four major HSPs with apparent molecular sizes of 70, 64, 15 and 14 kDa. Heat stress at 42.5 degrees C appeared to be the optimum temperature for HSP formation in cells grown at 30 degrees C. The relative rate of synthesis of HSP70 and HSP15 reached a maximum at 30 min after the temperature shift-up whereas the capability of cells to accumulate HSP64 and HSP14 continued through 2 h. The two most abundant HSPs, HSP70 and HSP64, were recognized on western blots by antibodies raised against authentic DnaK and GroEL from Escherichia coli. To furnish sufficient evidence for the assumption that HSP64 is a GroEL-related chaperonin, this protein was purified to homogeneity. There was a 76% sequence identity between the amino acid sequence of HSP64 and the corresponding protein in Synechococcus PCC 7942. Moreover, the purified HSP64 cross-reacted to anti-E. coli GroEL antibody. To our knowledge, this is the first report about the purification and partial protein sequencing of a cyanobacterial chaperonin.
Plant Mol Biol 1992 Jan
PMID:Heat shock protein synthesis of the cyanobacterium Synechocystis PCC 6803: purification of the GroEL-related chaperonin. 134 51

Mitochondria contain a nuclear-encoded heat shock protein, HSP60, which functions as a chaperonin in the post-translational assembly of multimeric proteins encoded by both nuclear and mitochondrial genes. We have isolated and sequenced full-length complementary DNAs coding for this mitochondrial chaperonin in Arabidopsis thaliana and Zea mays. Southern-blot analysis indicates the presence of a single hsp60 gene in the genome of A. thaliana. There is a high degree of homology at the predicted amino acid levels (43 to 60%) between plant HSP60s and their homologues in prokaryotes and other eukaryotes which indicates that these proteins must have similar evolutionarily conserved functions in all organisms. Northern- and western-blot analyses indicate that the expression of the hsp60 gene is developmentally regulated during seed germination. It is also heat-inducible. Developmental regulation of the (beta-subunit of F1-ATPase, an enzyme complex that is involved in the cyanide-sensitive mitochondrial electron transport system, indicates that imbibed embryos undergo rapid mitochondrial biogenesis through the early stages of germination. Based on the functional role of HSP60 in macromolecular assembly, these data collectively suggest that the presence of higher levels of HSP60 is necessary during active mitochondrial biogenesis, when the need for this protein is greatest in assisting the rapid assembly of the oligomeric protein structures.
Plant Mol Biol 1992 Mar
PMID:cDNA clones encoding Arabidopsis thaliana and Zea mays mitochondrial chaperonin HSP60 and gene expression during seed germination and heat shock. 134 37

The promoter region of the agarase gene (dagA) of Streptomyces coelicolor A3(2) is complex; it consists of four distinct promoters with different -10 and -35 regions. We report the isolation of a form of RNA polymerase that mediates transcription in vitro from the dagAp4 promoter. The core components of this RNA polymerase are associated with a polypeptide of c. 66 kDa; holoenzyme reconstitution experiments show that the 66 kDa polypeptide functions as a sigma factor that directs transcription from the dagAp4 and Bacillus subtilis veg promoters in vitro. Alignment of the DNA sequences of these two promoters shows that they have bases in common in the -10 and -35 regions and that these sequences are similar to those observed for the major RNA polymerases of other bacteria. N-terminal amino acid sequence analysis of the 66 kDa polypeptide revealed it to be the product of the hrdB gene. Previous experiments showed that the predicted amino acid sequence of the hrdB gene product is very similar to the major sigma factors of other bacteria and suggested that disruption of the hrdB gene is lethal. These observations together lead to the conclusion that we have isolated the major RNA polymerase of Streptomyces coelicolor A3(2). We have developed an improved protocol for the renaturation of sigma factors that have been isolated by preparative sodium dodecyl sulphate/polyacrylamide gel electrophoresis (SDS-PAGE). This method involves renaturing the polypeptide in the presence of the bacterial chaperonin GroEL. We expect this protocol to find general application for renaturation of other polypeptides that have been subjected to SDS-PAGE.
Mol Microbiol 1992 May
PMID:Isolation and characterization of the major vegetative RNA polymerase of Streptomyces coelicolor A3(2); renaturation of a sigma subunit using GroEL. 135 Mar 15

The nucleotide sequence of the luxA and luxB genes encoding the alpha beta heterodimeric luciferase from thermotolerant Vibrio harveyi CTP5 was determined. The DNA sequence of the CTP5 luxA and luxB genes is identical to the DNA sequence of the luxA and luxB genes from mesophilic V. harveyi MAV (B 392), with minor exceptions. The sequence differences result in 5 amino acid substitutions in the alpha subunit polypeptide and 7 amino acid substitutions in the beta subunit polypeptide. Escherichia coli cells grown on solid medium and expressing CTP5 or MAV luxAB genes emit similar amounts of light at 37 degrees C, while at 42 degrees C cells containing CTP5 luxAB genes show more than tenfold increased bioluminescence compared to cells with MAV luxAB genes. When grown in liquid medium E. coli cells with CTP5 or MAV luxAB genes emit equivalent amounts of light at 37 degrees C; however, in liquid medium at 42 degrees C cells containing CTP5 luxAB genes show only three times higher bioluminescence than cells with MAV luxAB genes. Expression of T7 promoter-linked hybrid luxAB transcriptional units luxACTP5-luxBMAV and luxAMAV-luxBCTP5 in E. coli reveals that (i) the MAV luxB gene product is responsible for the decreased activity of MAV luciferase at 42 degrees C; (ii) the CTP5 luxB gene encodes the information required for most of the increased activity of CTP5 luciferase relative to MAV luciferase at 42 degrees C; and (iii) E. coli cells containing MAV luxB gene show an increase in bioluminescence when grown in liquid medium at 42 degrees C, which coincides with elevated GroEL chaperonin levels.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Gen Genet 1991 Dec
PMID:The beta subunit polypeptide of Vibrio harveyi luciferase determines light emission at 42 degrees C. 168 11

Mitochondria contain a protein, hsp60, that is induced by heat shock and has been shown to function as a chaperonin in the assembly of mitochondrial enzyme complexes composed of proteins encoded by nuclear genes and imported from the cytosol. To determine whether products of mitochondrial genes are also assembled through an interaction with hsp60, we looked for association between hsp60 and proteins synthesized by isolated mitochondria. We have determined by electrophoretic, centrifugal, and immunological assays that at least two of those proteins become physically associated with hsp60. In mitochondrial matrix extracts, this association could be disrupted by the addition of Mg-ATP. One of the proteins that formed a stable association with hsp60 was the alpha subunit of the multicomponent complex F1-ATPase. We have not identified the other protein. These results indicate that hsp60 can function in the folding and assembly of mitochondrial proteins encoded by both mitochondrial and nuclear genes.
Mol Cell Biol 1990 Aug
PMID:Function of the maize mitochondrial chaperonin hsp60: specific association between hsp60 and newly synthesized F1-ATPase alpha subunits. 197 26

Two relatively abundant proteins having subunit molecular weights of 60,000 and 63,000 (p60 and p63, respectively) have been purified as a 16 to 18S complex from sperm mitochondria of a moth. Heliothis virescens. Although the function of these proteins had heretofore not been established, interest in the p63 polypeptide stemmed from its sperm-specific expression and its striking occurrence as a net charge variant among several insect species surveyed, using two-dimensional gel electrophoresis. Genomic and cDNA clones corresponding to the p63 protein have now been isolated and their sequencing has revealed extensive amino acid sequence identity with both the Escherichia coli GroEL protein and its eukaryotic homologues, the chaperonins. Immunoblot studies with a Tetrahymena chaperonin antiserum demonstrated that the p60 protein, which is expressed in all cell types, is structurally related to p63 and is itself a chaperonin subunit. While the chaperonin complex from Heliothis sperm shares certain properties with GroEL, including the ability to hydrolyze ATP and organization of its subunits into a seven-member ring, electron microscopic analysis revealed that its higher-order structure differed from GroEL (and other lower eukaryotic chaperonins) in that the native particle comprises one such ring rather than a doublet. It is not yet known whether the two chaperonin isoforms coexpressed in moth sperm assemble separately or give rise to hybrid particles. In either case, the existence of multiple chaperonin subunits in sperm leaves open the possibility that some aspect of mitochondrial biogenesis that is dependent upon the activity of these proteins is qualitatively or quantitatively different in this cell type.
J Mol Biol 1990 Jul 20
PMID:Identification and characterization of a testis-specific isoform of a chaperonin in a moth, Heliothis virescens. 197 8

Bacteriophage HK97 is a lambdoid phage with a head assembled from 415 copies of a 42 kDa subunit arranged in an icosahedrally symmetrical lattice with a triangulation number of 7. Prohead I, the first shell structure in the assembly pathway, is composed of 42 kDa coat protein subunits that have not yet undergone the proteolytic cleavage, conformational changes, and covalent cross-linking steps that occur later in the assembly of mature heads. Prohead I can be efficiently dissociated into capsomeres by treatment with 2 M KCl. The resulting capsomeres are a mixture of two species, identified as pentamers and hexamers of the 42 kDa subunit. These capsomeres were also detected as the products of chaperonin-assisted renaturation of 42 kDa polypeptide in vitro at room temperature or in the course of self folding and assembly in vitro at 0 degrees C. Pentamer and hexamer capsomeres can be interconverted in vitro by manipulating solvent conditions, and this makes it possible to carry out the in vitro shell assembly reaction at different input ratios of hexamer to pentamer. The Prohead I structures produced are always the normal (T = 7) size regardless of the input pentamer to hexamer ratio. Assembly is most efficient when the pentamer to hexamer ratio is 1:5 (a mass ratio of 1:6), or the same as the capsomere ratio in a T = 7 shell.
J Mol Biol 1995 Oct 13
PMID:Assembly in vitro of bacteriophage HK97 proheads. 747 18

A phylogenetic analysis of chaperonin (heat shock protein 60) sequences from prokaryotes and eukaryotes indicated that a single gene duplication event in the common ancestor of Mycobacterium tuberculosis, M. leprae, and Streptomyces albus gave rise to the duplicate chaperonin genes found in these species (designated HSP65 and GroEL in the mycobacterial species). Comparison of rates of synonymous and nonsynonymous nucleotide substitution in different gene regions suggested that the 5' end of the HSP65 gene was homogenized by an ancient recombination event between M. tuberculosis and M. leprae. In S. albus, the two duplicated chaperonin genes have evolved at essentially the same rate. In both M. tuberculosis and M. leprae, however, the GroEL gene has evolved considerably more rapidly at nonsynonymous nucleotide sites than has the HSP65 gene. Because this difference is not seen at synonymous sites, it must be due to a difference in selective constraint on the proteins encoded by the two genes, rather than to a difference in mutation rate. The difference between GroEL and HSP65 is striking in regions containing epitopes recognized by T cells of the vertebrate host; in certain cross-reactive epitopes conserved across all organisms, nonsynonymous sites in GroEL have evolved twice as fast as those in HSP65. It is suggested that these differences are correlated with differences in the way in which the duplicate chaperonins of M. tuberculosis and M. leprae interact with the host immune system.
Mol Biol Evol 1993 Nov
PMID:Contrasting evolutionary rates in the duplicate chaperonin genes of Mycobacterium tuberculosis and M. leprae. 750 44

Based on 16S rDNA sequence comparison, intracellular mycetome-associated endosymbionts (P-endosymbionts) of tsetse flies (Diptera: Glossinidae) form a distinct lineage within the gamma-3 subdivision of proteobacteria, related to the free-living bacterium Escherichia coli, midgut S-endosymbionts of various insects including tsetse flies, and to the P-endosymbiont lineage of aphids, Buchnera aphidicola. Gene organization and expression of several loci in intracellular microorganisms have revealed differences from free-living bacteria. This study analyses two of these characteristics in tsetse endosymbionts; the copy number and gene organization of rDNA operations and the nature of the abundant protein(s) synthesized by these microorganisms. Results indicate that Glossina morsitans morsitans S-endosymbionts have multiple (seven) rDNA operons coding for 16S (rrs) followed by 23S (rrl) gene sequences, whereas tsetse P-endosymbionts have a single, similarly organized rDNA operon. In tsetse mycetocytes in vitro, P-endosymbionts synthesize a predominant protein of 60 kDa in size (p60) which by Western blot analysis shows immunological cross-reactivity with the abundant 63 kDa (p63) protein of B. aphidicola. p63 (also referred to as symbionin) has been characterized as a molecular chaperone, structurally and functionally similar to the groEL protein of E. coli. Under in vitro conditions, tsetse S-endosymbionts synthesize high levels of a similarly-sized protein that cross-reacts with p63 chaperonin. Antisera against the tsetse p60 protein also recognizes p63 protein of B. aphidicola, suggesting that the abundant tsetse endosymbiont protein is a chaperonin.
Insect Mol Biol 1995 Feb
PMID:Molecular analysis of the endosymbionts of tsetse flies: 16S rDNA locus and over-expression of a chaperonin. 753 12

We identified and isolated a Saccharomyces cerevisiae gene which, when overexpressed, suppressed the temperature-sensitive phenotype of cells expressing a mutant allele of the gene encoding the mitochondrial chaperonin, Hsp60. This gene, SCS1 (suppressor of chaperonin sixty-1), encodes a 757-amino-acid protein of as yet unknown function which, nonetheless, has human, rice, and Caenorhabditis elegans homologs with high degrees (ca. 60%) of amino acid sequence identity. SCS1 is not an essential gene, but SCS1-null strains do not grow above 37 degrees C and show some growth-related defects at 30 degrees C as well. This gene is expressed at both 30 and 38 degrees C, producing little or no differences in mRNA levels at these two temperatures. Overexpression of SCS1 could not complement an HSP60-null allele, indicating that suppression was not due to the bypassing of Hsp60 activity. Of 10 other hsp60-ts alleles tested, five could also be suppressed by SCS1 overexpression. There were no common mutant phenotypes of the strains expressing these alleles that give any clue as to why they were suppressible while others were not. An epitope (influenza virus hemagglutinin)-tagged form of SCS1 in single copy complemented an SCS1-null allele. The Scs1-hemagglutinin protein was found to be at comparable levels and in similar multiply modified forms in cells growing at both 30 and 38 degrees C. Surprisingly, when localized either by cell fractionation procedures or by immunocytochemistry, these proteins were found not in mitochondria but in the cytosol. The overexpression of SCS1 had significant effects on the cellular levels of mRNAs encoding the proteins Cpn10 and Mgel, two other mitochondrial protein cochaperones, but not on mRNAs encoding a number of other mitochondrial or cytosolic proteins analyzed. The implications of these findings are discussed.
Mol Cell Biol 1995 Oct
PMID:SCS1, a multicopy suppressor of hsp60-ts mutant alleles, does not encode a mitochondrially targeted protein. 756 13


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