Escherichia coli DnaJ and GrpE heat shock proteins jointly stimulate ATPase activity of DnaK

The products of the Escherichia coli dnaK, dnaJ, and grpE heat shock genes have been previously shown to be essential for bacteriophage lambda DNA replication at all temperatures and for bacterial survival under certain conditions. DnaK, the bacterial heat shock protein hsp70 analogue and putative chaperonin, possesses a weak ATPase activity. Previous work has shown that ATP hydrolysis allows the release of various polypeptides complexed with DnaK. Here we demonstrate that the ATPase activity of DnaK can be greatly stimulated, up to 50-fold, in the simultaneous presence of the DnaJ and GrpE heat shock proteins. The presence of either DnaJ or GrpE alone results in a slight stimulation of the ATPase activity of DnaK. The action of the DnaJ and GrpE proteins may be sequential, since the presence of DnaJ alone leads to an acceleration in the rate of hydrolysis of the DnaK-bound ATP. The presence of GrpE alone increases the rate of release of bound ATP or ADP without affecting the rate of hydrolysis. The stimulation of the ATPase activity of DnaK may contribute to its more efficient recycling, and it helps explain why mutations in dnaK, dnaJ, or grpE genes often exhibit similar pleiotropic phenotypes.

Polypeptide flux through bacterial Hsp70: DnaK cooperates with trigger factor in chaperoning nascent chains

A role for DnaK, the major E. coli Hsp70, in chaperoning de novo protein folding has remained elusive. Here we show that under nonstress conditions DnaK transiently associates with a wide variety of nascent and newly synthesized polypeptides, with a preference for chains larger than 30 kDa. Deletion of the nonessential gene encoding trigger factor, a ribosome-associated chaperone, results in a doubling of the fraction of nascent polypeptides interacting with DnaK. Combined deletion of the trigger factor and DnaK genes is lethal under normal growth conditions. These findings indicate important, partially overlapping functions of DnaK and trigger factor in de novo protein folding and explain why the loss of either chaperone can be tolerated by E. coli.

Initiation of lambda DNA replication with purified host- and bacteriophage-encoded proteins: the role of the dnaK, dnaJ and grpE heat shock proteins

Based on previous in vivo genetic analysis of bacteriophage lambda growth, we have developed two in vitro lambda DNA replication systems composed entirely of purified proteins. One is termed 'grpE-independent' and consists of supercoiled lambda dv plasmid DNA, the lambda O and lambda P proteins, as well as the Escherichia coli dnaK, dnaJ, dnaB, dnaG, ssb, DNA gyrase and DNA polymerase III holoenzyme proteins. The second system includes the E.coli grpE protein and is termed 'grpE-dependent'. Both systems are specific for plasmid molecules carrying the ori lambda DNA initiation site. The major difference in the two systems is that the 'grpE-independent' system requires at least a 10-fold higher level of dnaK protein compared with the grpE-dependent one. The lambda DNA replication process may be divided into several discernible steps, some of which are defined by the isolation of stable intermediates. The first is the formation of a stable ori lambda-lambda O structure. The second is the assembly of a stable ori lambda-lambda O-lambda P-dnaB complex. The addition of dnaJ to this complex also results in an isolatable intermediate. The dnaK, dnaJ and grpE proteins destabilize the lambda P-dnaB interaction, thus liberating dnaB's helicase activity, resulting in unwinding of the DNA template. At this stage, a stable DNA replication intermediate can be isolated, provided that the grpE protein has acted and/or is present. Following this, the dnaG primase enzyme recognizes the single-stranded DNA-dnaB complex and synthesizes RNA primers. Subsequently, the RNA primers are extended into DNA by DNA polymerase III holoenzyme. The proposed model of the molecular series of events taking place at ori lambda is substantiated by the many demonstrable protein-protein interactions among the various participants.

Rapid Drink Challenge in high-resolution manometry: an adjunctive test for detection of esophageal motility disorders

BACKGROUND/AIMS

The Chicago Classification for diagnosis of esophageal motility disorders by high-resolution manometry (HRM) is based on single water swallows (SWS). Emerging data suggest that a "Rapid Drink Challenge" (RDC) increases sensitivity for motility disorders. This study establishes normal values and diagnostic thresholds for RDC in clinical practice.

METHODS

Two cohort studies were performed in patients with dysphagia or reflux symptoms (development and validation sets). Healthy subjects and patient controls provided reference values. Ten SWS and two 200-mL RDC were performed. Primary diagnosis for SWS was established by the Chicago Classification. Abnormal RDC was defined by impaired esophagogastric junction (EGJ) function (elevated integrated relaxation pressure during RDC [IRP-RDC]); incomplete inhibition of contractility during and ineffective contraction after RDC. Diagnostic thresholds identified in the development set were prospectively tested in the validation set.

RESULTS

Normal values were determined in healthy (n=95; age 37.8 ± 12) and patient controls (n=44; age 46.4 ± 15). Development and validation sets included 178 (54 ± 17 years) and 226 (53 ± 16 years) patients, respectively. Integrated relaxation pressure during RDC was higher for SWS than RDC in all groups (overall P<.001), except achalasia. Rapid Drink Challenge suppressed contractility, except in achalasia type III, spasm, and hypercontractile motility disorders (P<.001). An effective after-contraction was present more often in health than disease (P<.001). Optimal diagnostic thresholds identified in the development set (IRP-RDC ≥12 mmHg achalasia, IRP-RDC ≥ 8mmHg "all cause" EGJ dysfunction), were confirmed in the validation set (both, sensitivity ~85%, specificity >95%).

CONCLUSIONS

Rapid Drink Challenge contributes clinically relevant information to routine HRM studies, especially in patients with EGJ dysfunction.

The heat-shock-regulated grpE gene of Escherichia coli is required for bacterial growth at all temperatures but is dispensable in certain mutant backgrounds

Previous work has established that the grpE+ gene product is a heat shock protein that is essential for bacteriophage lambda growth at all temperatures and for Escherichia coli growth at temperatures above 43 degrees C. Here it is shown that the grpE+ gene product is essential for bacterial viability at all temperatures. The strategy required constructing a grpE deletion derivative carrying a selectable chloramphenicol drug resistance marker provided by an omega insertion and showing that this deletion construct can be crossed into the bacterial chromosome if and only if a functional grpE+ gene is present elsewhere in the same cell. As a control, the same omega insertion could be placed immediately downstream of the grpE+ coding sequence without any observable effects on host growth. This result demonstrates that the inability to construct a grpE-deleted E. coli strain is not simply due to a lethal polar effect on neighboring gene expression. Unexpectedly, it was found that the grpE deletion derivative could be crossed into the bacterial chromosome in a strain that was defective in DnaK function. Further analysis showed that it was not the lack of DnaK function per se that allowed E. coli to tolerate a deletion in the grpE+ gene. Rather, it was the presence of unknown extragenic suppressors of a dnaK mutation that somehow compensated for the deficiency in both DnaK and GrpE function.

Mobile elements bounded by C4A4 telomeric repeats in Oxytricha fallax

A novel family of micronuclear elements termed telomere-bearing elements (TBEs) is described. All 1900 family members are eliminated during macronuclear development. We conclude that they are transposons, first because the members are moderately conserved in sequence and probably dispersed in the genome. Second, in two cases, sequence comparison of the termini and flanks of the element with the corresponding empty site indicate that elements cause 3 bp target duplications (AAT) upon insertion; the 3 bp are part of the 5 bp target sequence, AATGA. Lastly, both elements carry 77 or 78 bp inverted terminal repeats. The tip of each inverted terminal repeat is the 17 bp telomere-like sequence 5' C1A4C4A4C4. At least half of the elements have these 17 bp or an extremely similar sequence. One possible pathway for transposition into new micronuclear sites starts in the developing macronucleus with excision to create a free linear form to which telomeres are added, followed by a low frequency of movement to the micronucleus, and insertion into the germ-line micronuclear DNA.

Isolation and characterization of dnaJ null mutants of Escherichia coli

Bacteriophage lambda requires the lambda O and P proteins for its DNA replication. The rest of the replication proteins are provided by the Escherichia coli host. Some of these host proteins, such as DnaK, DnaJ, and GrpE, are heat shock proteins. Certain mutations in the dnaK, dnaJ, or grpE gene block lambda growth at all temperatures and E. coli growth above 43 degrees C. We have isolated bacterial mutants that were shown by Southern analysis to contain a defective, mini-Tn10 transposon inserted into either of two locations and in both orientations within the dnaJ gene. We have shown that these dnaJ-insertion mutants did not grow as well as the wild type at temperatures above 30 degrees C, although they blocked lambda DNA replication at all temperatures. The dnaJ-insertion mutants formed progressively smaller colonies at higher temperatures, up to 42 degrees C, and did not form colonies at 43 degrees C. The accumulation of frequent, uncharacterized suppressor mutations allowed these insertion mutants to grow better at all temperatures and to form colonies at 43 degrees C. None of these suppressor mutations restored the ability of the host to propagate phage lambda. Radioactive labeling of proteins synthesized in vivo followed by immunoprecipitation or immunoblotting with anti-DnaJ antibodies demonstrated that no DnaJ protein could be detected in these mutants. Labeling studies at different temperatures demonstrated that these dnaJ-insertion mutations resulted in altered kinetics of heat shock protein synthesis. An additional eight dnaJ mutant isolates, selected spontaneously on the basis of blocking phage lambda growth at 42 degrees C, were shown not to synthesize DnaJ protein as well. Three of these eight spontaneous mutants had gross DNA alterations in the dnaJ gene. Our data provide evidence that the DnaJ protein is not absolutely essential for E. coli growth at temperatures up to 42 degrees C under standard laboratory conditions but is essential for growth at 43 degrees C. However, the accumulation of extragenic suppressors is necessary for rapid bacterial growth at higher temperatures.

Escherichia coli grpE gene codes for heat shock protein B25.3, essential for both lambda DNA replication at all temperatures and host growth at high temperature

We have identified the grpE gene product as the B25.3 heat shock protein of Escherichia coli on the following evidence: (i) a protein similar in size and isoelectric point to B25.3 was induced after infection of UV-irradiated bacteria by lambda grpE+ transducing phage, (ii) mutant phage lambda grpE40, isolated by its inability to propagate on grpE280 bacteria, failed to induce the synthesis of the B25.3 protein, and (iii) lambda grpE+ revertants, derived from phage grpE40 as able to propagate on grpE280 bacteria, simultaneously recovered the ability to induce synthesis of the B25.3 protein. In addition, we show that E. coli bacteria carrying the grpE280 mutation are temperature sensitive for bacterial growth at 43.5 degrees C. Through transductional analysis and temperature reversion experiments, it was demonstrated that the grpE280 mutation is responsible for both the inability of lambda to replicate at any temperature tested and the lack of colony formation at high temperature. At the nonpermissive temperature the rates of synthesis of DNA and RNA were reduced in grpE280 bacteria.

Motilin-induced gastric contractions signal hunger in man

RATIONALE

Hunger is controlled by the brain, which receives input from signals of the GI tract (GIT). During fasting, GIT displays a cyclical motor pattern, the migrating motor complex (MMC), regulated by motilin.

OBJECTIVES

To study the relationship between hunger and MMC phases (I-III), focusing on spontaneous and pharmacologically induced phase III and the correlation with plasma motilin and ghrelin levels. The role of phase III was also studied in the return of hunger after a meal in healthy individuals and in patients with loss of appetite.

FINDINGS

In fasting healthy volunteers, mean hunger ratings during a gastric (62.5±7.5) but not a duodenal (40.4±5.4) phase III were higher (p<0.0005) than during phase I (27.4±4.7) and phase II (37±4.5). The motilin agonist erythromycin, but not the cholinesterase inhibitor neostigmine, induced a premature gastric phase III, which coincided with an increase in hunger scores from 29.2±7 to 61.7±8. The somatostatin analogue octreotide induced a premature intestinal phase III without a rise in hunger scores. Hunger ratings significantly correlated (β=0.05; p=0.01) with motilin plasma levels, and this relationship was lost after erythromycin administration. Motilin, but not ghrelin administration, induced a premature gastric phase III and a rise in hunger scores. In contrast to octreotide, postprandial administration of erythromycin induced a premature gastric phase III accompanied by an early rise in hunger ratings. In patients with unexplained loss of appetite, gastric phase III was absent and hunger ratings were lower.

CONCLUSIONS

Motilin-induced gastric phase III is a hunger signal from GIT in man.

Sequence analysis and transcriptional regulation of the Escherichia coli grpE gene, encoding a heat shock protein

We have sequenced the Escherichia coli grpE gene and shown that it encodes a 197-amino acid residue protein of 21,668-Mr. The predicted N-terminal amino acid sequence, as well as the overall amino acid composition agree well with that of the purified protein. From Northern analysis, we have shown that transcription of the grpE gene is under heat shock regulation, i.e., there is a rapid and transient increase in the rate of synthesis of grpE mRNA upon a shift-up in temperature. Forty-six bases upstream of the structural gene is a sequence closely related to the consensus heat shock promoter identified by Cowing et al. [Proc. Natl. Acad. Sci. U.S.A, 82, 2679-2683]. We have shown by S1 mapping and RNA sequencing that this is indeed the promoter for the grpE mRNA. It appears that all discernable transcription initiates only from this promoter, even under non-heat shock conditions.

Review article: endpoints used in functional dyspepsia drug therapy trials

BACKGROUND

The measurement of patient-reported outcomes (PRO) in treatment trials for functional gastrointestinal disorders is a matter of controversy.

AIM

To focus on instruments and endpoints that have been used to evaluate the efficacy of therapeutic agents in functional dyspepsia (FD) trials, also considering the newly defined Rome III FD criteria.

METHODS

A Medline search was conducted to identify relevant studies pertaining to FD treatment, with particular emphasis on the studies to date which have used validated outcome measures.

RESULTS

Currently available outcome measures are heterogeneous across studies. They include global binary endpoints, analogue or categorical scoring scales, uni- or multi-dimensional disease specific questionnaires, global outcome evaluations and quality of life questionnaires. Across the available outcome measures, substantial heterogeneity is found, not only in the type of endpoint measure, but also in the number and types of symptoms that are considered to be part of the FD symptom complex. Especially based on content validity, none of the existing questionnaires or endpoints can be considered sufficiently validated to be recommended unequivocally as the primary outcome measure for FD trials according to the Rome III criteria. On the other hand, existing well-validated multi-dimensional questionnaires that include many non-FD symptoms can be narrowed down to evaluate only the cardinal symptoms according to Rome III.

CONCLUSIONS

There is an urgent need to develop Rome III-based patient-reported outcomes for functional dyspepsia. Well-validated multi-dimensional questionnaires may serve as a guidance for this purpose, and could also be considered for use in ongoing clinical trials.

Using the Earth as a polarized electron source to search for long-range spin-spin interactions

Many particle-physics models that extend the standard model predict the existence of long-range spin-spin interactions. We propose an approach that uses the Earth as a polarized spin source to investigate these interactions. Using recent deep-Earth geophysics and geochemistry results, we create a comprehensive map of electron polarization within the Earth induced by the geomagnetic field. We examine possible long-range interactions between these spin-polarized geoelectrons and the spin-polarized electrons and nucleons in three laboratory experiments. By combining our model and the results from these experiments, we establish bounds on torsion gravity and possible long-range spin-spin forces associated with the virtual exchange of either spin-one axial bosons or unparticles.

Genetic analysis of bacteriophage-encoded cochaperonins

Early genetic studies identified the Escherichia coli groES and groEL genes because mutations in them blocked the growth of bacteriophages lambda and T4. Subsequent genetic and biochemical analyses have shown that GroES and GroEL constitute a chaperonin machine, absolutely essential for E. coli growth, because it is needed for the correct folding of many of its proteins. In spite of very little sequence identity to GroES, the bacteriophage T4-encoded Gp31 protein and the bacteriophage RB49-encoded CocO protein are bona fide GroEL cochaperonins, even capable of substituting for GroES in E. coli growth. A major functional distinction is that only Gp31 and CocO can assist GroEL in the correct folding of Gp23, the major bacteriophage capsid protein. Conserved structural features between CocO and Gp31, which are absent from GroES, highlight their potential importance in specific cochaperonin function.

Influence of ghrelin on the gastric accommodation reflex and on meal-induced satiety in man

Ghrelin increases gastric tone in the fasting state and enhances gastric emptying in gastroparesis. The aims of the study were to evaluate the effect of ghrelin on postprandial gastric tone and on meal-induced satiety in health. Ten healthy volunteers underwent a barostat study on two occasions. After determination of intra-abdominal pressure (minimal distending pressure, MDP), isobaric volume measurement was performed for 90 min at MDP + 2 mmHg. After 20 min, ghrelin (40 microg) or saline was administered i.v. over 30 min in a double-blind-randomized cross-over design, followed 10 min later by a liquid meal (200 mL, 300 kcal). Stepwise isobaric distentions (+2 mmHg per 2 min) were performed 60 min after the meal. Data (mean +/- SEM) were compared using paired Student's t-test and ANOVA. Separately, a satiety drinking test (15 mL min(-1) until satiety score 5) was performed on 10 subjects twice, after treatment with placebo or ghrelin. Ghrelin infusion significantly inhibited gastric accommodation (mean volume increase adjusted means 108.0 +/- 50 vs 23.0 +/- 49 mL, P = 0.03, ANCOVA with the premeal postinfusion volume as covariate) and reduced postprandial gastric volumes (197.2 +/- 24.6 vs 353.5 +/- 50.0 mL, P = 0.01). Pressures inducing perception or discomfort during postprandial gastric distentions were not altered. During satiety testing, ghrelin did not alter nutrient volume ingested till maximal satiety (637.5 +/- 70.9 vs 637.5 +/- 56.2 mL, ns). Ghrelin administered during the meal significantly inhibits gastric accommodation in health, but this is not associated with early satiation.

Isolation and characterization of point mutations in the Escherichia coli grpE heat shock gene

The Escherichia coli grpE gene (along with dnaK, dnaJ, groEL, and groES) was originally identified as one of the host factors required for phage lambda growth. The classical grpE280 mutation was the only grpE mutation that resulted from the initial screen and shown to specifically block the initiation of lambda DNA replication. Here we report the isolation of several new grpE missense mutations, again using phage lambda resistance as a selection. All mutants fall into two groups based on their temperature-dependent phenotype for lambda growth. Members of the first group (I), including grpE17 and grpE280, which was obtained again, are resistant to lambda growth at both 30 and 42 degrees C. Members of the second group (II), including grpE25, grpE66, grpE103, grpE13a, grpE57b, and grpE61, are sensitive to lambda growth at 30 degrees C but resistant at 42 degrees C. All mutations are recessive, since an E. coli grpE null mutant strain carrying these mutant alleles on low-copy-number plasmids are sensitive to infection by the lambda grpE+ transducing phage. Both group I and group II mutants are temperature sensitive for E. coli growth above 42 degrees C. The nucleotide changes were identified by sequencing analyses and shown to be dispersed throughout the latter 75% of the grpE coding region. Most of the amino acid changes occur at conserved residues, as judged by sequence comparisons between E. coli and other bacterial and yeast GrpE homologs. The isolation of these new mutations is the first step toward a structure-function analysis of the GrpE protein.

The spectrum of motor function abnormalities in gastroesophageal reflux disease and Barrett's esophagus

Barrett's esophagus has traditionally been regarded as the most severe end of the spectrum of gastroesophageal reflux disease and is of great clinical importance in view of the association with esophageal adenocarcinoma. Studies have documented high levels of esophageal acid exposure in Barrett's esophagus. Various pathogenetic mechanisms underlie this phenomenon. These include abnormalities in esophageal peristalsis, defective lower esophageal sphincter pressures, gastric dysmotility and bile reflux. Whilst these factors provide evidence for an acquired cause of Barrett's esophagus, an underlying genetic predisposition cannot be ruled out. Although the past decade has brought about many new discoveries in the pathogenesis of Barrett's esophagus, it has also added further controversy to this complex disorder. A detailed analysis of the gastrointestinal motor abnormalities occurring in Barrett's esophagus follows, with a review of the currently available literature and an update on this condition that continues to be of interest to the gastroenterologist.

Measurement of gastric accommodation: a reappraisal of conventional and emerging modalities

Impaired gastric accommodation is an important cause of functional dyspepsia. Currently available tests that evaluate gastric accommodation provide relevant physiological information, but they pose technical difficulties and their clinical impact remains controversial. Gastric barostat remains the gold standard, but it is an invasive procedure. In recent years, emerging modalities including single photon emission computed tomography (SPECT), three-dimensional ultrasound and magnetic resonance imaging have been developed to measure gastric volumes and hold promise as alternative methods of assessing gastric accommodation non-invasively. Studies are underway to validate these techniques with recent data proving the performance characteristics of SPECT. The non-invasive nutrient drink test measures satiety scores as a surrogate marker of gastric accommodation and remains controversial. More recently, intragastric monitoring has been proposed as yet another non-invasive modality to assess gastric accommodation. Each of these different modalities brings its associated advantages and disadvantages, as is discussed in this review. Ongoing studies to validate these new techniques are in progress and are likely to lead to further progress in neurogastroenterology.

Pseudo-T-even bacteriophage RB49 encodes CocO, a cochaperonin for GroEL, which can substitute for Escherichia coli's GroES and bacteriophage T4's Gp31

Bacteriophage T4-encoded Gp31 is a functional ortholog of the Escherichia coli GroES cochaperonin protein. Both of these proteins form transient, productive complexes with the GroEL chaperonin, required for protein folding and other related functions in the cell. However, Gp31 is specifically required, in conjunction with GroEL, for the correct folding of Gp23, the major capsid protein of T4. To better understand the interaction between GroEL and its cochaperonin cognates, we determined whether the so-called "pseudo-T-even bacteriophages" are dependent on host GroEL function and whether they also encode their own cochaperonin. Here, we report the isolation of an allele-specific mutation of bacteriophage RB49, called epsilon22, which permits growth on the E. coli groEL44 mutant but not on the isogenic wild type host. RB49 epsilon22 was used in marker rescue experiments to identify the corresponding wild type gene, which we have named cocO (cochaperonin cognate). CocO has extremely limited identity to GroES but is 34% identical and 55% similar at the protein sequence level to T4 Gp31, sharing all of the structural features of Gp31 that distinguish it from GroES. CocO can substitute for Gp31 in T4 growth and also suppresses the temperature-sensitive phenotype of the E. coli groES42 mutant. CocO's predicted mobile loop is one residue longer than that of Gp31, with the epsilon22 mutation resulting in a Q36R substitution in this extra residue. Both the CocO wild type and epsilon22 proteins have been purified and shown in vitro to assist GroEL in the refolding of denatured citrate synthase.

Mitochondrial GrpE is present in a complex with hsp70 and preproteins in transit across membranes

We characterized a 24-kDa protein associated with matrix hsp70 (mt-hsp70) of Neurospora crassa and Saccharomyces cerevisiae mitochondria. By using specific antibodies, the protein was identified as MGE, a mitochondrial homolog of the prokaryotic heat shock protein GrpE. MGE extracted from mitochondria was quantitatively bound to hsp70. It was efficiently released from hsp70 by the addition of Mg-ATP but not by nonhydrolyzable ATP analogs or high salt. A mutant mt-hsp70, which was impaired in release of bound precursor proteins, released MGE in an ATP-dependent manner, indicating that precursor proteins and MGE bind to different sites of hsp70. A preprotein accumulated in transit across the mitochondrial membranes was specifically coprecipitated by either antibodies directed against MGE or antibodies directed against mt-hsp70. The preprotein accumulated at the outer membrane was not coprecipitated by either antibody preparation. After being imported into the matrix, the preprotein could be coprecipitated only by antibodies against mt-hsp70. We propose that mt-hsp70 and MGE cooperate in membrane translocation of preproteins.

Mutational analysis of the phage T4 morphogenetic 31 gene, whose product interacts with the Escherichia coli GroEL protein

The phage T4 morphogenetic gene 31 has been sequenced. Its deduced gene product is a polypeptide of 111 aa, with a predicted Mr of 12064 and a pI of 4.88. The proof that the assigned open reading frame (ORF) encodes Gp31 rests on the sequencing of two known gene 31 amber mutations, amN54 and NG71, demonstrating that these mutations result in translational termination within the assigned ORF. Furthermore, the sequencing of four different T4 epsilon mutations, isolated on the basis of allowing the phage to propagate on Escherichia coli groEL- hosts, showed that they are either missense mutations or 3-bp deletions in the gene 31 reading frame. The sequencing of neighboring DNA revealed the presence of five other ORFs, one of which overlaps gene 31 substantially, but in the opposite orientation.

Isolation and characterization of the Escherichia coli htrD gene, whose product is required for growth at high temperatures

Those genes in Escherichia coli defined by mutations which result in an inability to grow at high temperatures are designated htr, indicating a high temperature requirement. A new htr mutant of E. coli was isolated and characterized and is designated htrD. The htrD gene has been mapped to 19.3 min on the E. coli chromosome. Insertional inactivation of htrD with a mini-Tn10 element resulted in a pleiotropic phenotype characterized by a severe inhibition of growth at 42 degrees C and decreased survival at 50 degrees C in rich media. Furthermore, htrD cells were sensitive to H2O2. Growth rate analysis revealed that htrD cells grow very slowly in minimal media supplemented with amino acids. This inhibitory effect has been traced to the presence of cysteine in the growth medium. Further studies indicated that the rate of cysteine transport is higher in htrD cells relative to the wild type. All of these results, taken together, indicate that the htrD gene product may be required for proper regulation of intracellular cysteine levels and that an increased rate of cysteine transport greatly affects the growth characteristics of E. coli.

The essential Escherichia coli msgB gene, a multicopy suppressor of a temperature-sensitive allele of the heat shock gene grpE, is identical to dapE

The grpE gene product is one of three Escherichia coli heat shock proteins (DnaK, DnaJ, and GrpE) that are essential for both bacteriophage lambda DNA replication and bacterial growth at all temperatures. In an effort to determine the role of GrpE and to identify other factors that it may interact with, we isolated multicopy suppressors of the grpE280 point mutation, as judged by their ability to reverse the temperature-sensitive phenotype of grpE280. Here we report the characterization of one of them, designated msgB. The msgB gene maps at approximately 53 min on the E. coli chromosome. The minimal gene possesses an open reading frame that encodes a protein with a predicted size of 41,269 M(r). This open reading frame was confirmed the correct one by direct amino-terminal sequence analysis of the overproduced msgB gene product. Genetic experiments demonstrated that msgB is essential for E. coli growth in the temperature range of 22 to 37 degrees C. Through a sequence homology search, MsgB was shown to be identical to N-succinyl-L-diaminopimelic acid desuccinylase (the dapE gene product), which participates in the diaminopimelic acid-lysine pathway involved in cell wall biosynthesis. Consistent with this finding, the msgB null allele mutant is viable only when the growth medium is supplemented with diaminopimelic acid. These results suggest that GrpE may have a previously unsuspected function(s) in cell wall biosynthesis in E. coli.

Initiation of lambda DNA replication reconstituted with purified lambda and Escherichia coli replication proteins

Using highly purified bacteriophage lambda and E. coli replication proteins, we were able to reconstitute an in vitro system capable of replication ori lambda-containing plasmid DNA. The addition of a new E. coli factor, the grpE gene product, to this replication system reduced the level of dnaK protein required for efficient DNA synthesis by at least 10-fold, and also allowed the isolation of a stable DNA replication intermediate. Based on all available information, we propose a molecular mechanism for the action of the dnaK and grpE proteins during the prepriming reaction leading to lambda DNA synthesis.

Diagnosis, etiology, and therapy of fibromyalgia

Fibromyalgia is characterized by diffuse pain, multiple tender points, fatigue, and sleep disturbance. Its frequent concurrence with rheumatic diseases modifies the clinical picture of the "primary" disease. This article reviews new information about the etiopathogenesis and treatment of this syndrome.