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Biomedical subjects

S A Thompson

Publications and source records attributed to S A Thompson.

At least 91 records · Page 5Linked to original sources
PubMed1997

Craniofacial growth after iatrogenic cleft palate repair in a fetal ovine model.

Controversy exists over the impact of scar formation on craniofacial growth after cleft palate repair. The fetal ovine model presents an opportunity to study a group of animals with little or no scar using cephalometric studies of cranio-facial growth after iatrogenic cleft palate repair. Grossly evident scar is formed in the palates of lambs repaired at 118 days or later in gestation, while those animals operated at 70 and 77 days' gestation exhibited no scar grossly and minimal scar histologically in the submucosa with normal nasal and oral mucosal surfaces. For this study, 15 lambs were studied: four were unoperated, three were operated at 70 days, one at 77 days, and seven had clefts produced and repaired at 118 to 133 days' gestation. The animals were euthanized at 1 month of age and the heads removed and frozen until analyzed. Computerized tomography of the heads was used to create voxel (volume pixel) data sets, and volume rendering and measurement software (Voxblast) was used to create a three-dimensional reconstruction of the skull. Palate measurements were obtained by selecting points on the upper deciduous premolars. A plane was set through the palate and upper deciduous premolars using standard points on the skull to maintain consistent visualization and point selection. The measurements were normalized to skull size measured by the distance between points on the right and left zygomatic bones. Using one-way analysis of variance, followed by a protected t test, no significant differences were found between the means of any measurement in the three treatment groups. Fetal palate repair, with or without scarring, resulted in normal craniofacial growth in the 1-month-old lamb.

Analysis of Variance↗
PubMed1997

Continuity of care: University of Iowa Cleft Lip/Palate Interdisciplinary Team.

INTRODUCTION: Patient satisfaction with the continuity of care is an important aspect of care delivery that may be evaluated to assess team effectiveness. This study was conducted to evaluate the number of patients seen by each team member, and the patients' perceived importance of continued care by the same health care provider during their overall treatment. METHODS: A survey was constructed by the members of the Cleft Lip/Palate Team at the University of Iowa Hospitals and Clinics. One hundred and thirty-eight subjects were invited to participate during consecutive clinic days over a 5-month period; 101 subjects (73.1%) responded. RESULTS: The survey revealed that the percentage of patients seen by each member of the team ranged from 92.1% (93/101) for the surgeon to 24.8% (25/101) for the genetic counselor. Strong agreement with continuity of care by health professionals ranged from 85.6% (83/97) for the surgeon, 63.7% (58/91) for the orthodontist, 63% (17/27) for the psychologist, to 23.1% (19/82) for the audiologist. The percentages dropped somewhat if the patients thought that they may have to wait longer for their next appointment. CONCLUSION: There is a strong preference for continuity of health care.

Adolescent↗
PubMed1997

Differences in agonist/antagonist binding affinity and receptor transduction using recombinant human gamma-aminobutyric acid type A receptors.

Using human gamma-aminobutyric acid type A (GABAA) receptor subunit combinations, expressed in cell lines and Xenopus laevis oocytes, the pharmacology of a number of ligands interacting directly with the GABA recognition site has been studied in [3H]muscimol binding and electrophysiologically. The binding affinity of GABAA agonist and antagonist ligands showed small but statistically significant dependence on the subunit composition of receptors that include gamma 2 and different alpha and beta subunits. The potency of antagonist ligands was largely independent of receptor subunit composition, whereas the composition of receptors expressed in oocytes strongly influenced the EC50 value of agonists. An apparent reciprocal correlation between subunits favoring agonist binding and antagonist binding, respectively, was observed. Whereas antagonists showed comparable potencies in binding and functional studies, the potency of agonists in binding studies was generally two to three orders of magnitude higher than the agonist potencies measured electrophysiologically. 5-(4-Piperidyl)isothiazol-3-ol, which behaves as a low efficacy partial agonist at GABAA receptors in cultured cortical neurons, showed no efficacy in oocytes, but produced pure antagonist effects with a binding/functional affinity ratio between those observed for the agonists and antagonists. It is concluded that the GABAA receptor mechanisms transducing binding into physiological response, but not the binding per se, is dependent on the receptor subunit composition.

Animals↗
PubMed1996

COOH-terminal extended recombinant amphiregulin with bioactivity comparable with naturally derived growth factor.

The mature secreted form of the epidermal growth factor (EGF) receptor ligand amphiregulin (AR) is reported to be an 84-amino acid residue polypeptide, which is generated by proteolytic processing of a 252-amino acid precursor. This form of recombinant AR (rAR84) and two forms with COOH-terminal extensions corresponding to sequences from the AR precursor (rAR87 and rAR92) were expressed at high levels in Escherichia coli, oxidized to the correct disulfide arrangement, and purified to homogeneity. rAR84 competed poorly for binding of radiolabeled EGF to the EGF receptor and had little ability to stimulate growth of Balb/c/3T3 cells. In striking contrast, rAR87 and rAR92 possessed 42- and 20-fold greater receptor binding activity and 55- and 14-fold greater bioactivity, respectively. Furthermore, addition of the COOH-terminal four amino acids from transforming growth factor alpha to the COOH terminus of rAR84 improved the activity of rAR84 by 100- and 1000-fold, respectively, in these assays. rAR87 was found to have approximately 32% of the specific activity of natural AR from MCF-7 cells when compared in two different bioassays. These findings strongly suggest that the 84-amino acid sequence is not the correct structure of the naturally occurring secreted form of AR and that natural AR contains additional amino acid residues at the COOH-terminal end.

3T3 Cells↗
PubMed1996

STAT activation by epidermal growth factor (EGF) and amphiregulin. Requirement for the EGF receptor kinase but not for tyrosine phosphorylation sites or JAK1.

The epidermal growth factor (EGF) receptor activates several signaling cascades in response to the ligands EGF and amphiregulin (AR). One of these signaling events involves the tyrosine phosphorylation of STATs (signal transducers and activators of transcription), a process believed to require the activation of a tyrosine kinase of the JAK family. In this report we demonstrate that EGF- and AR-induced STAT activation requires the intrinsic kinase activity of the receptor but not the presence of Jak1. We show that both wild type (WT) and truncated EGF receptors lacking all autophosphorylation sites activate STAT 1, 3, and 5 in response to either EGF or AR. Furthermore, relative to cells expressing WT receptor, ligand-induced tyrosine phosphorylation of the STATs was enhanced in cells expressing only the truncated receptor. These results provide the first evidence that (i) EGF receptor-mediated STAT activation occurs in a Jak1-independent manner, (ii) the intrinsic tyrosine kinase activity of the receptor is essential for STAT activation, and (iii) tyrosine phosphorylation sites within the EGF receptor are not required for STAT activation.

Amphiregulin↗
PubMed1996

Structure and chromosomal location of the mouse interleukin-12 p35 and p40 subunit genes.

Interleukin-12 (IL-12) is a heterodimeric cytokine composed of p35 and p40 subunits and is required for induction of T helper 1 (Th1) responses. Knowledge of how the IL-12 gene is regulated will permit an understanding of susceptibility and resistance to pathogenic microbes and to autoiummune diseases. In this report, we provide the gene structures, nucleotide sequences and chromosomal assignment for the p35 and p40 subunits of mouse IL-12. The p35 and p40 subunit genes are distributed over 8 kb and 14 kb, and map to chromosomes 3 and 11, respectively. The p35 subunit gene consists of eight exons, including a 5'-noncoding exon that was defined by sequence comparison of genomic DNA with the 5'ends of novel cDNA molecules. Transcription of p35 mRNA can start from the first exon but can also initiate further downstream. Potential transcription regulatory elements, AP1, AP2, AP3, NF-kB and GATA recognition sequences, are located within 523 bp upstream of the p35 gene; however, no TATA box was identified. The p40 subunit gene consists of eight exons. A TATA box is located 30 bp upstream from the transcription start site, and AP1, AP3, GATA, and Pu.1 recognition sequences are located within 690 bp upstream of the p40 gene. An AGTTTCTACTTT sequence, which acts as an interferon-gamma response element in the promoter of the major histocompatibility complex class I gene, was also found upstream of the p40 gene.

Animals↗
PubMed1996

Localization of gamma-glutamylcysteine synthetase mRNA expression in mouse brain following methylmercury treatment using reverse transcription in situ PCR amplification.

In previous studies we reported that prolonged treatment of rats with subtoxic levels of mercury as methymercury hydroxide (MMH) elicited a two- to three-fold increase in renal glutathione (GSH) content and a three- to fourfold increase in the mRNA encoding the catalytically active heavy subunit of gamma-glutamylcysteine synthetase (GCS), the rate-limiting enzyme in GSH synthesis. Since methylmercury is a potent neurotoxicant, we investigated the effect of methylmercury treatment on GSH synthesis and the distribution of GCS mRNA expression in the brain. Male C57B1/ 6 mice were treated for 3 consecutive days with MMH (3 mg/kg/ day,i.p.). GSH levels in whole brains were increased by twofold 24 hr following the first injection and remained elevated two to three times control levels after two subsequent MMH treatments. Concomitantly, whole brain GCS mRNA levels were increased 2.7-fold 24 hr after the third MMH treatment. Reverse transcription in situ PCR amplification of GCS heavy subunit mRNA in brain slices taken from MMH-treated mice showed that GCS expression was selectively localized to the cerebellum and hippocampal regions and, within these regions, to areas which are known to resist methylmercury toxicity. In contrast, no GCS mRNA expression was found in brain regions which are known to be highly susceptible to mercury toxicity. These findings suggest that resistance to methylmercury toxicity in the brain may reflect the ability of specific neuronal cell types to up-regulate GSH synthesis as a protective response to mercury-mediated cell damage.

Animals↗
PubMed1996

Localization by in situ hybridization of gamma-glutamylcysteine synthetase mRNA expression in rat kidney following acute methylmercury treatment.

In previous studies we reported that prolonged treatment of rats with subtoxic levels of mercury as methylmercury hydroxide (MMH) elicited a two- to threefold increase in renal glutathione (GSH) content and a three- to fourfold increase in the mRNA encoding the catalytically active heavy subunit of gamma-glutamylcysteine synthetase (GCS), the rate-limiting enzyme in GSH synthesis. In the present studies, we demonstrate that enhanced expression of GCS mRNA and GSH synthesis rapidly occur following acute MMH treatment and, moreover, that increased expression of renal GCS mRNA is localized predominantly to regions of the kidney cortex consistent with the principal distribution of mercury in the kidney. Previous studies have demonstrated that resistance to mercury toxicity during prolonged MMH exposure may be associated with the ability to up-regulate GSH synthesis subsequent to intracellular dealkylation of MMH to Hg2+. The present finding that GCS mRNA and GSH levels are rapidly increased in kidney cells which are most susceptible to mercury toxicity supports the view that up-regulation of GSH synthesis occurs as an initial adaptive response to Hg2(+)-mediated cytotoxicity following acute as well as prolonged mercury exposure.

Animals↗
PubMed1996

Oral commissure burns in children.

Electrical burns of the mouth are relatively common in young children. Early intervention to prevent complications remains controversial. A chart review was conducted of 24 patients with oral commissure burns who were treated at the University of Iowa from 1975 to 1988. All of these patients were treated conservatively without splinting or early surgery. Only one patient underwent oral splinting before receiving care at the University of Iowa Hospitals and Clinics. While under our care, no patients suffered significant hemorrhage at eschar separation. Commissuroplasty and/or reconstructive lip surgery were performed at various times after the burn injury was healed and the functional or aesthetic impairment was established. Long-term follow-up was from 5 to 17 years, allowing for longitudinal evaluation of the postburn scars and their influence on facial growth. Our review revealed that (1) younger children with more severe burns have a less favorable outcome; (2) no hemorrhage was observed immediately after the burn or at eschar separation; and (3) conservative surgical treatment after scar maturation- and in some cases following steroid injections- resulted in a successful functional and esthetic outcome.

Burns, Electric↗
PubMed1996

Craniofacial growth in rabbits after rigid or semi-rigid fixation of the frontonasal suture.

Treatment of craniofacial dysostosis involves complex remodeling of the cranium and facial bones. Maintenance of the newly positioned segments may be achieved by rigid fixation using plates; however, there is concern that, over time, these plates may interfere with normal growth. The purpose of this study was to test a method of "semi-rigid" fixation of an osteotomy of the frontonasal suture in juvenile rabbits by comparing standardized parameters of craniofacial growth after conventional suture plating with the experimental plating method and with growth after sham operation. Forty-five, 6-week-old, weanling rabbits were divided into three groups of 15 each (12 for cephalometry, 3 for histological examination): (group 1) control, sham operated; (group 2) rigid fixation; (group 3) semi-rigid fixation. Rabbits were maintained for 14 weeks. Craniofacial growth was assessed using three-dimensional image analysis techniques. Measurements were subjected to statistical analysis (one-way analysis of variance) to compare the three treatment groups. Pairwise comparison of means between the treatment groups was done using Bonferroni's method at the 0.05 significance level. Semi-rigid fixation permitted significantly more normal growth of the developing rabbit head than rigid fixation in total snout length, total vault length, left and right midface height, and left orbital length. Both semi-rigid and rigid fixation significantly restricted growth compared with sham operated animals in left and right posterior midface height, right orbital length, right and left nasal bone length, and left parietal width. There were no significant differences in the growth of all other parameters measured.

Animals↗
PubMed1996

Barbiturate interactions at the human GABAA receptor: dependence on receptor subunit combination.

1. Human GABAA receptors containing different alpha and beta subunits with a gamma 2s subunit were expressed in Xenopus oocytes and the effects of pentobarbitone on these subunit combinations were examined by electrophysiological recording of GABA currents with the two-electrode voltage-clamp method. 2. Pentobarbitone has previously been shown to have three actions on GABAA receptors: a potentiation of GABA responses, a direct activation of GABAA receptors and, at high concentrations, a block of the GABA chloride channel. In this study pentobarbitone activity consisted of the above mentioned three components on all the subunit combinations tested. However, the affinities and efficacies varied with receptor subtype. 3. Potentiation of GABA by pentobarbitone occurred over the same concentration-range for all the subunits with affinities in the range of 20-35 microM. The degree of potentiation obtained, however, varied from 236% of GABA EC20 on alpha 1 beta 2 gamma 2s to 536% on alpha 6 beta 2 gamma 2s. 4. Examination of the direct effect of pentobarbitone revealed that the type of alpha subunit present determines both the degree of affinity and efficacy obtained. Receptors containing an alpha 6 subunit produced maximum direct responses to pentobarbitone larger than that obtainable with maximum GABA (150% to 170% of maximum GABA). The maximum direct pentobarbitone response obtainable with other alpha subunits ranged between 45% of maximum GABA for alpha 5 beta 2 gamma 2s to 82% for alpha 2 beta 2 gamma 2s. The affinity of the direct action of pentobarbitone on alpha 6 beta 2 gamma 2s was 58 microM compared to affinities for the other alpha subunits ranging from 139 microM on alpha 2 beta 2 gamma 2s to 528 microM on alpha 5 beta 2 gamma 2s. 5. The type of beta subunit present did not influence the direct action of pentobarbitone to the same extent as the alpha subunit. There were no significant differences between affinity or efficacy on oocytes expressing alpha 6 and gamma 2s with beta 1, beta 2 or beta 3. Affinities and efficacies on oocytes expressing alpha 1 and gamma 2s with beta 1, beta 2 or beta 3 were significantly different with pentobarbitone having a higher affinity and efficacy on alpha 1 beta 3 gamma 2s followed by alpha 1 beta 2 gamma 2s and then alpha 1 beta 1 gamma 2s. 6. The direct effect of pentobarbitone was blocked by picrotoxin but not by competitive antagonists, such as bicuculline or SR95531, indicating that the direct agonist activity of pentobarbitone was not mediated via the GABA binding site. 7. For the first time the influence of the various alpha and beta subunits on the effects of pentobarbitone were demonstrated. The results indicate that GABAA receptors containing alpha 6 subunits have both a higher affinity and efficacy for direct activation by pentobarbitone, and reveal that pentobarbitone binds to more than one site on the GABAA receptor, and these are dependent on receptor subunit composition.

Animals↗
PubMed1996

Functional characterization of human gamma-aminobutyric acidA receptors containing the alpha 4 subunit.

The alpha subunits are an important determinant of the pharmacology of gamma-aminobutyric acidA (GABAA) receptors with respect to agonists, antagonists, and modulatory compounds, particularly the benzodiazepines. The alpha 4 subunit is the least abundant subunit in the brain and the most similar in deduced primary amino acid sequence to the alpha 6 subunit. We demonstrate that the human alpha 4 subunit forms a functional receptor when expressed with beta gamma 2, demonstrating some properties similar to alpha 6 beta gamma 2 and some properties more akin to alpha 1 beta gamma 2. It also exhibited some properties that were unlike any other alpha subunit-containing receptor. GABA affinity seemed to be identical to that of the alpha 1 beta 1 gamma 2 receptor; however, the partial agonists 4,5,6,7-tetrahydroisoxazolo-[5,4-c]pyridin-3-ol and piperidine-4-sulfonic acid showed lower efficacy than at either alpha 1 beta 1 gamma 2 or alpha 6 beta 1 gamma 2. Benzodiazepine pharmacology of alpha 4-containing receptors was similar to that of alpha 6-containing receptors with the exception of dimethoxy-4-ethyl-beta-carboline-3-carboxylate, which behaved as a partial inverse agonist. Pentobarbital potentiated alpha 4 beta 1 gamma 2 receptor GABA responses to a level comparable with alpha 6 beta 1 gamma 2 (approximately 700% of EC20); however, unlike alpha 6 beta 1 gamma 2 receptors, it did not elicit any direct activation of the receptor. Propofol also potentiated alpha 4 beta 1 gamma 2 GABA responses but to a level more comparable to that of alpha 1 beta 1 gamma 2, suggesting that these compounds act via different sites. Unlike other subunit combinations, propofol did not elicit a direct activation of the receptor. These results suggest that the mechanism for direct activation of the GABAA receptor by pentobarbital and propofol is absent on alpha 4-containing receptors. Furosemide, which non-competitively inhibits the GABAA receptor, showed 700-fold selectivity for alpha 6 beta 3 gamma 2 receptors over alpha 1-, alpha 2-, alpha 3-, and alpha 5-containing receptors and exhibited selectivity for alpha 4 beta 3 gamma 2 receptors (> 50-fold). These experiments reveal a unique pharmacology for alpha 4-containing receptors with some similarities to both alpha 6- and alpha 1-containing receptors.

Amino Acid Sequence↗
PubMed1995

Nucleotide sequence of the Aspergillus niger srpA gene.

The Aspergillus niger (An) gene srpA, encoding a protein with homology to the signal recognition particle (SRP) 54-kDa protein from Saccharomyces cerevisiae (Sc), has been isolated and the nucleotide sequence determined. The putative An srpA gene is comprised of two exons of 78 and 1527 bp separated by a 49-bp intron, and encodes a protein of 534 amino acids that is 53% identical to Sc SRP54.

Amino Acid Sequence↗
PubMed1995

Expression and pharmacology of human GABAA receptors containing gamma 3 subunits.

A cDNA encoding the gamma 3 subunit of the human GABAA receptor has been obtained by molecular cloning. Its deduced amino acid sequence shows a high level of sequence identity with the published mouse and rat sequences (96%). The ligand binding pharmacology of the benzodiazepine site formed by stably-expressed human alpha 5 beta 3 gamma 2S and alpha 5 beta 3 gamma 3 GABAA receptor subtypes have been compared for a number of ligands, Benzodiazepine site ligands were found to be either non-selective or gamma 2-selective, with the exception of CL218,872, which was found to be 10-fold selective for the alpha 5 beta 3 gamma 3-containing subtype Two benzodiazepine site ligands. Ro15-4513 and FG8205 were more efficacious at alpha 5 beta 3 gamma 3 receptors than alpha 5 beta 3 gamma 2 receptors expressed in Xenopus oocytes, CL218,872, which is a partial agonist at alpha 1 containing receptors, had no intrinsic activity at either alpha 5 beta 3 gamma 2 or alpha 5 beta 3 gamma 3, alpha 1 beta 2 gamma 2S and alpha 1 beta 2 gamma 3 human GABAA receptors were also expressed in Xenopus oocytes and their benzodiazepine pharmacology investigated. Both the EC50 and efficacy of benzodiazepine site ligands were influenced by the type of gamma subunit coexpressed with alpha 1 and beta 2.

Amino Acid Sequence↗
PubMed1995

Heregulin activation of extracellular acidification in mammary carcinoma cells is associated with expression of HER2 and HER3.

HER2, the erbB-2/neu proto-oncogene product, is a 185-kDa transmembrane glycoprotein related to the epidermal growth factor receptor. Overexpression of HER2 was reported in several human adenocarcinomas, including mammary and ovarian carcinomas. A family of glycoproteins, the heregulin/neu differentiation factors, was characterized and implicated as the ligands for HER2. Recently, it has been shown that HER2 alone is not sufficient to reconstitute high affinity heregulin receptors and that HER3 or HER4 may be the required components of the heregulin receptors on mammary carcinoma cells (Sliwkowski, M.X., Schaefer, G., Akita, R.W., Lofgren, J.A., Fitzpatrick, V.D., Nuijens, A., Fendly, B.M., Cerione, R.A., Vandlen, R.L., and Carraway, K.L., III (1994) J. Biol. Chem. 269, 14661-14665; Plowman, G.D., Green, J.M., Culouscou, J.-M., Carlton, G.W., Rothwell, V.M., and Buckley, W. (1993) Nature 366, 473-475). Using the Cytosensor to measure the extracellular acidification rate, we have examined the effects of recombinant human heregulin-alpha on three mammary carcinoma cell lines expressing HER2 (MDA-MB-453, SK-BR-3, and MCF-7), an ovarian carcinoma cell line expressing HER2 (SK-OV-3), and CHO-K1 and 293-EBNA cells stably transfected with HER2. By reverse transcription polymerase chain reaction and Western blotting, we found that the breast cells also express HER3 and that the ovarian line co-expresses the HER4 message. A dramatic increase in the acidification rate was observed for the mammary carcinoma cells co-expressing high levels of HER2 and HER3. In contrast, the ovarian cells expressing high levels of HER2 and low levels of HER4 or CHO-K1 and 293-EBNA cells expressing HER2 alone were not responsive to heregulin. When these same transfected cells were exposed to monoclonal anti-HER2 antibody followed by anti-IgG to cause aggregation of the HER2 molecules, an increase in the acidification rate was observed, indicating coupling of transfected HER2 to the signal transduction pathway. Transfection of HER2 into MCF-7 cells, on the other hand, gave 4-fold enhanced acidification responses. These data, together with the previously reported high affinity heregulin binding and activation of tyrosine phosphorylation in HER2 and HER3 co-transfected cells support the role of HER2 and HER3 as components of the heregulin receptor in breast cells.

Animals↗
PubMed1995

Assessing the shape of root canals: an in vitro method using microradiography.

The aim of this paper is to describe an in vitro method which provides clear and accurate details of root canal shape. The method utilizes the technique of contact microradiography to produce high resolution, two-dimensional, real-size images of canals in a longitudinal plane. Specimens can be accurately rotated through 90 degrees allowing images to be produced in a bucco-lingual and mesio-distal direction. The method is simple, relatively rapid and can process large numbers of teeth without the need for complicated and expensive mounting blocks or film holders. The technique can be used to produce pre- and post-operative images of canal shape which can be superimposed to delineate the dentine removed during canal preparation. The method is thus suitable for the evaluation of the shaping ability of endodontic instruments and preparation techniques.

Dental Pulp Cavity↗
PubMed1995

Isolation of the Helicobacter pylori recA gene and involvement of the recA region in resistance to low pH.

To understand the potential roles of the important DNA repair protein RecA in Helicobacter pylori pathogenesis, we cloned the recA gene from H. pylori 84-183. Degenerate PCR primers based on conserved RecA protein regions were used to amplify a portion of H. pylori recA, which was used as a probe to isolate the full-length recA gene from H. pylori genomic libraries. The H. pylori recA gene encoded a protein of 347 amino acids with a molecular mass of 37.6 kDa. As expected, H. pylori RecA was highly similar to other RecA proteins and most closely resembled that of Campylobacter jejuni (75% identity). Immediately downstream of recA was an open reading frame whose predicted product showed 58% identity to the Bacillus subtilis enolase protein. recA and eno were disrupted in H. pylori 84-183 by insertion of antibiotic resistance genes. Reverse transcription-PCR demonstrated that recA and eno were cotranscribed and that insertion of the kanamycin resistance gene into recA had polar effects on expression of the downstream eno. The H. pylori recA mutants were severely impaired in their ability to survive treatment with UV light and methyl methanesulfonate and with the antimicrobial agents ciprofloxacin and metronidazole. The eno mutant had sensitivities to UV light and metronidazole intermediate to those of wild-type and recA strains, suggesting that truncation of the recA-eno transcript resulted in lowered recA expression. For survival at low pH, a recA mutant was approximately 10-fold more sensitive than strain 84-183, while the eno mutant demonstrated intermediate susceptibility. This difference occurred in the presence or absence of urea, implying the involvement of a gene in the recA region in an acid resistance mechanism distinct from that mediated by urease.

Amino Acid Sequence↗