[Pilot study: Apricena Marble District quarry workers and COPD]

The aim of the present article was to verify the Chronic Obstructive Pulmonary Disease (COPD) prevalence in a cohort of quarry workers who belong to the Apricena Marble District. We studied 70 workers. They received a questionnaire about the disease and confounding factors. The spirometry showed that the FEV1 was normal in 95% of workers, instead 5% showed values lower than former (Average: 73%). TNF alpha and IL-1 Beta in Exhaled breath condensate (EBC) were lower than the method limit in all workers. Our cohort is limited, but we could retain that the lung disease is not present in workers taken into consideration. Our results are in according to Rushton who demonstrated that only a prolonged occupation, higher than thirty years, is able to induce lung disease.

Molecular and functional characterization of polynucleotide phosphorylase from the antarctic eubacterium Pseudoalteromonas haloplanktis

Polyribonucleotide phosphorilase from the psychrophilic Antarctic eubacterium Pseudoalteromonas haloplanktis (PhPNPase) has been purified. This enzyme catalyzes both the RNA polymerisation and degradation reaction, showing the highest activity at temperatures below 40 degrees C. PhPNPase is quite sensitive to heat treatment and it is endowed with remarkable halotolerance.

Independent prognostic value of fascin immunoreactivity in stage III-IV colonic adenocarcinoma

Fascin, an actin-bundling protein involved in cell motility, has been shown to be upregulated in several types of carcinomas. In this study, we investigated the expression of fascin in 228 advanced colonic adenocarcinoma patients with a long follow-up. Fascin expression was compared with several clinicopathologic parameters and survival. Overall, fascin immunoreactivity was detected in 162 (71%) tumours with a prevalence for right-sided tumours (P<0.001). Fascin correlated significantly with sex, tumour grade and stage, mucinous differentiation, number of metastatic lymph nodes, extranodal tumour extension, and the occurrence of distant metastases. Patients with fascin-expressing tumours experienced a shorter disease-free and overall survival in comparison with those with negative tumours, and fascin immunoreactivity emerged as an independent prognostic factor in the multivariate analysis. Moreover, patients with the same tumour stages could be stratified in different risk categories for relapse and progression according to fascin expression. Our findings suggest that fascin is a useful prognostic marker for colonic adenocarcinomas.

Peptide receptors in neuroendocrine tumors of the lung as potential tools for radionuclide diagnosis and therapy

Neuroendocrine tumors of the lung are carcinomas characterized by different impact on the patients' prognosis, ranging from relatively indolent, low- to intermediate-grade neoplasms with longer life expectation (i.e., typical and atypical carcinoids) to very aggressive and poorly differentiated neoplasms with dismal prognosis (i.e., large cell neuroendocrine carcinoma and small cell lung cancer). The standard treatment of typical or atypical carcinoids is the complete surgical resection, whereas the role of radio-chemotherapy in a multimodality treatment or for palliation remains controversial. Conversely, high-grade neuroendocrine carcinomas are in primis treated by aggressive combination chemotherapy, deserving surgical resection for uncommon low-stage tumors. Since evidence has been accumulated that neuroendocrine tumors of the lung are supplied with a wide array of peptide receptors detectable on cell membranes by immunohistochemical methods, innovative strategies for diagnosis and radiometabolic therapy have been devised to target these molecules for the correct clinical management of the patients. In this paper, the structural and functional aspects and the clinical applications of the detection of several peptide receptors in pulmonary neuroendocrine tumors will be reviewed, including somatostatin receptors, vasoactive intestinal peptide/pituitary adenylate cyclase activating peptide family receptors, cholecystokinin /gastrin receptors, bombesin/gastrin releasing peptide receptors, neurotensin receptors, substance P receptors, neuroepeptide Y receptors, calcitonin/calcitonin gene-related peptide receptors, atrial natriuretic peptide receptors, glucagon-like-peptide-1 receptors, oxytocin receptors and endothelin receptors. Only a detailed knowledge of the peptide receptor distribution in these tumor types, especially in uncommon neoplasms such as atypical carcinoids and large cell neuroendocrine carcinomas, is pivotal for planning the most adequate interventions for the patients' diagnosis and therapy.

Psychrophilic superoxide dismutase from Pseudoalteromonas haloplanktis: biochemical characterization and identification of a highly reactive cysteine residue

A psychrophilic superoxide dismutase (SOD) has been characterized from the Antarctic eubacterium Pseudoalteromonas haloplanktis (Ph). PhSOD is a homodimeric iron-containing enzyme and displays a high specific activity, even at low temperature. The enzyme is inhibited by sodium azide and inactivated by hydrogen peroxide; it is also very sensitive to peroxynitrite, a physiological inactivator of the human mitochondrial Mn-SOD. Even though PhSOD is isolated from a cold-adapted micro-organism, its heat stability is well above the maximum growth temperature of P. haloplanktis, a feature common to other Fe- and Mn-SODs. The primary structure of PhSOD was determined by a combination of mass spectrometry and automated Edman degradation. The polypeptide chain is made of 192 amino acid residues, corresponding to a molecular mass of 21251 Da. The alignment with other Fe- and Mn-SODs showed a high amino acid identity with Fe-SOD from Vibrio cholerae (79%) and Escherichia coli (70%). A significant similarity is also shared with human mitochondrial Mn-SOD. PhSOD has the unique and highly reactive Cys57 residue, located in a variable region of the protein. The three-dimensional model of the PhSOD monomer indicates that Cys57 is included in a region, whose structural organization apparently discriminates between dimeric and tetrameric SODs. This residue forms a disulfide adduct with beta-mercaptoethanol, when this reducing agent is added in the purification procedure. The reactivity of Cys57 leads also to the formation of a disulfide bridge between two PhSOD subunits in specific denaturing conditions. The possible modification of Cys57 by physiological thiols, eventually regulating the PhSOD functioning, is discussed.

Partial purification and MALDI-TOF MS analysis of UN1, a tumor antigen membrane glycoprotein

UN1 is a membrane glycoprotein that is expressed in immature human thymocytes, a subpopulation of peripheral T lymphocytes, the HPB acute lymphoblastic leukemia (ALL) T-cell line and fetal thymus. We previously reported the isolation of a monoclonal antibody (UN1 mAb) recognizing the UN1 protein that was classified as "unclustered" at the 5th and 6th International Workshop and Conference on Human Leukocyte Differentiation Antigens. UN1 was highly expressed in breast cancer tissues and was undetected in non-proliferative lesions and in normal breast tissues, indicating a role for UN1 in the development of a tumorigenic phenotype of breast cancer cells. In this study, we report a partial purification of the UN1 protein from HPB-ALL T cells by anion-exchange chromatography followed by immunoprecipitation with the UN1 mAb and MALDI-TOF MS analysis. This analysis should assist in identifying the amino acid sequence of UN1.

[Descriptive statistics of occupational accidents during 2005 in the area of competency of the Occupational Health Unit FG/1]

During 2005, the Unit of Occupational Health of the Local Health Centre FG/1 started to record accident at work. The results confirme "Industry" as the sector with the highest risk of accidents at work. Many accidents at work seem to be in relation with the insufficient use of D.P.I. or with the wrong use of D.P.I. The results point out the necessity of a better model to record data and in particular the data that describe what/how has the accident happened and the sector/subsector of workers. In order to continue this activity during the next years, it will be useful to control the trend.

A 35 kDa NAD(P)H oxidase previously isolated from the archaeon Sulfolobus solfataricus is instead a thioredoxin reductase

A thioredoxin reductase (TrxR) has been identified in the hyperthermophilic archaeon Sulfolobus solfataricus (Ss). This enzyme is a homodimeric flavoprotein that was previously identified as NADH oxidase in the same micro-organism ('Biotechnol. Appl. Biochem. 23 (1996) 47'). The primary structure of SsTrxR is made of 323 amino acid residues and contains two putative betaalphabeta regions for the binding of FAD, and a NADP(H) binding consensus sequence in the proximity of a CXXC motif. These findings indicate that SsTrxR is structurally related to the class II of the pyridine nucleotide-disulphide oxidoreductases family. Moreover, the enzyme exhibits a NADP(H) dependent thioredoxin reductase activity requiring the presence of FAD. Surprisingly, the reductase activity of SsTrxR is reduced in the presence of a specific inhibitor of mammalian TrxR. This finding demonstrates that the archaeal enzyme, although structurally related to eubacterial TrxR, is functionally closer to eukaryal enzymes. Experimental evidences indicate that a disulphide bridge is required for the reductase but also for the NADH oxidase activity of the enzyme. These results are further supported by the significantly reduced activities exerted by the C147A mutant. The integrity of the CXXC motif is also involved in the stability of the enzyme.

Breast cancer diagnosed during pregnancy and lactation: biological features and treatment options

AIM OF THE STUDY

Assessment of biological features and treatment of patients with breast cancer presenting during pregnancy or lactation.

PATIENTS AND METHODS

Immunohistochemical analysis of estrogen receptor (ER) and progesterone receptor (PgR), Ki-67, HER2/neu, prognostic markers, treatment and follow-up of 21 patients with breast cancer during pregnancy (BCdP) and 17 with breast cancer during lactation (BCdL) are presented.

RESULTS

Median age was 36 and 33 years, median tumour size was 2.4 and 2.5 cm, axillary lymph nodes were positive in 10 of 21 pregnant patients and 11 of 17 lactating patients, respectively. Both ER and PgR were not expressed in six of 21 pregnant women and nine of 17 lactating patients. All the six women who had concurrent diagnosis of breast cancer and pregnancy (first trimester) preferred termination of pregnancy although an alternative option was discussed. Five patients received anthracycline containing chemotherapy during the second and third trimester with no complications for patient and child. Conservative surgery was performed in 15 of 21 patients during pregnancy with no local reappearance after a median follow-up of 24 months. Three pregnant women underwent lymphoscintigraphy and sentinel lymph node biopsy.

CONCLUSIONS

Patients who had concurrent diagnosis of breast cancer and pregnancy (early first trimester) preferred termination of pregnancy to allow easier completion of treatment. Conservative surgery was safe also in women with BCdP. Sentinel node biopsy might be considered for pregnant patients with a clinically negative axilla.

[Considerations about health risk management]

From the birth of doctrines of Risk Management to today a lot of time is passed. From the initial application in the field of the insurances and the management of the enterprises, theories inspired to the identification, evaluation and correction of connected risks to the activity and the industrial trial has been figurative to the health, field in which the application of these principles results to be how much never profit and productive of benefits above all for the patients that suffer consequences of errors but also for the physicians and the personnel that, perfectly inserted in an organization aware of the trials to put into effect, can bring their contribution to underline the weak points of the relief trial. The economic cost and consequences of errors can decrease if a new culture is established inspired to the learning and the communication of the adverse events, to minimize the possibility that they again occurs.

Salts induce structural changes in elongation factor 1alpha from the hyperthermophilic archaeon Sulfolobus solfataricus: a Fourier transform infrared spectroscopic study

Elongation factor 1alpha from the hyperthermophilic archaeon Sulfolobus solfataricus (SsEF-1alpha) carries the aminoacyl tRNA to the ribosome; it binds GDP or GTP, and it is also endowed with an intrinsic GTPase activity that is triggered in vitro by NaCl at molar concentrations [Masullo, M., De Vendittis, E., and Bocchini, V. (1994) J. Biol. Chem. 269, 20376-20379]. The structural properties of SsEF-1alpha were investigated by Fourier transform infrared spectroscopy. The estimation of the secondary structure of the SsEF-1alpha*GDP complex, made by curve fitting of the amide I' band or by factor analysis of the amide I band, indicated a content of 34-36% alpha-helix, 35-40% beta-sheet, 14-19% turn, and 7% unordered structure. The substitution of the GDP bound with the slowly hydrolyzable GTP analogue Gpp(NH)p induced a slight increase in the alpha-helix and beta-sheet content. On the other hand, the alpha-helix content of the SsEF-1alpha*GDP complex increased upon addition of salts, and the highest effect was produced by 5 M NaCl. The thermal stability of the SsEF-1alpha*GDP complex was significantly reduced when the GDP was replaced with Gpp(NH)p or in the presence of NaBr or NH4Cl, whereas a lower destabilizing effect was provoked by NaCl and KCl. Therefore, the extent of the destabilizing effect of salts depended on the nature of both the cation and the anion. The data suggested that the sodium ion was responsible for the induction of the GTPase activity, whereas the anion modulated the enzymatic activity through destabilization of particular regions of SsEF-1alpha. Finally, the infrared data suggested that, in particular region(s) of the polypeptide chain, the SsEF-1alpha*Gpp(NH)p complex possesses structural conformations which are different from those present in the SsEF-1alpha*GDP complex.

Cardiopulmonary exercise test in young women affected by anorexia nervosa

BACKGROUND

The aim of this study was to evaluate exercise performance in patients affected by anorexia nervosa.

METHODS

We studied 19 patients (all females, mean age 23.1 +/- 5.2 years) affected by anorexia nervosa (mean weight 37.3 kg, body mass index 14.04 +/- 1.4 kg/m2) and 20 constitutionally thin women, matched for age, height and physical activity, with a body mass index < 19 kg/m2. All these women underwent clinical examination, standard ECG and a cardiopulmonary stress test.

RESULTS

Patients affected by anorexia nervosa showed a lower heart rate and systolic blood pressure at peak exercise (148.8 +/- 13.8 vs 171 +/- 9.2 b/min, p < 0.001, and 130 +/- 9.5 vs 152 +/- 11.2 mmHg, p < 0.001), work load (85.5 +/- 15.1 vs 117.2 +/- 20.3 W, p < 0.001), rate-pressure product (19 371 +/- 2391 vs 25,986 +/- 2218 b/min/mmHg, p < 0.001), oxygen uptake (VO2) at rest and maximum VO2 (5.4 +/- 1.7 vs 7.1 +/- 1.1 ml/kg/min, p < 0.001, and 28.08 +/- 6.3 vs 40.2 +/- 7.1 ml/kg/min, p < 0.001), anaerobic threshold (15.7 +/- 1.9 vs 20.4 +/- 2.1 ml/kg/min, p < 0.001), VO2 during exercise (9.5 +/- 1.2 vs 12.8 +/- 1.3 ml/min/W, p < 0.001), maximum minute ventilation (34.5 +/- 9.9 vs 48.4 +/- 10.3 /min, p < 0.001), and oxygen pulse (7.2 +/- 2 vs 10.9 +/- 2.4 ml/b, p < 0.001).

CONCLUSIONS

These data show an abnormal working capacity and cardiovascular responses to exercise in patients affected by anorexia nervosa. The low VO2, both at rest and during exercise, allows them to maintain a relatively high level of physical activity, which contributes to increase the energy expenditure needed for weight loss.

Phenylmethanesulfonyl fluoride inactivates an archaeal superoxide dismutase by chemical modification of a specific tyrosine residue. Cloning, sequencing and expression of the gene coding for Sulfolobus solfataricus superoxide dismutase

The gene encoding the superoxide dismutase from the hyperthermophilic archaeon Sulfolobus solfataricus (SsSOD) was cloned and sequenced and its expression in Escherichia coli obtained. The chemicophysical properties of the recombinant SsSOD were identical with those of the native enzyme. The recombinant SsSOD possessed a covalent modification of Tyr41, already observed in native SsSOD [Ursby, T., Adinolfi, B.S., Al-Karadaghi, S., De Vendittis, E. & Bocchini, V. (1999) J. Mol. Biol. 286, 189--205]. HPLC analysis of SsSOD samples prepared from cells treated or not with phenylmethanesulfonyl fluoride (PhCH(2)SO(2)F), a protease inhibitor routinely added during the preparation of cell-free extracts, showed that the modification was caused by PhCH(2)SO(2)F. Refinement of the crystal model of SsSOD confirmed that a phenylmethanesulfonyl moiety was attached to the hydroxy group of Tyr41. PhCH(2)SO(2)F behaved as an irreversible inactivator of SsSOD; in fact, the specific activity of both native and recombinant enzyme decreased as the percentage of modification increased. The covalent modification caused by PhCH2SO2F reinforced the heat stability of SsSOD. These results show that Tyr41 plays an important role in the enzyme activity and the maintenance of the structural architecture of SsSOD.

Psychrophilic elongation factor Tu from the antarctic Moraxella sp. Tac II 25: biochemical characterization and cloning of the encoding gene

The elongation factor Tu was isolated from a psychrophilic eubacterial Antarctic Moraxella strain (MoEF-Tu) and its molecular and functional properties were determined. It catalyzed the synthesis of poly(Phe) and bound specifically guanine nucleotides with an affinity for GDP about 12-fold higher than that for GTP. The affinity toward guanine nucleotides was lower than that of other eubacterial EF-Tu. The intrinsic GTPase activity of MoEF-Tu was hardly detectable but was accelerated by 2 orders of magnitude in the presence of the antibiotic kirromycin (GTPase(k)). Such a property resembled Escherichia coli EF-Tu (EcEF-Tu) even though the affinity of MoEF-Tu for the antibiotic was lower. MoEF-Tu showed a thermophilicity higher than that of EcEF-Tu; its temperature for half-denaturation was 44 degrees C. The MoEF-Tu encoding gene corresponding to E. coli tufA was cloned and sequenced. The translated protein had a calculated molecular weight of 43 288 and contained the GTP-binding sequence motifs. Concerning its primary structure, MoEF-Tu showed sequence identity with E. coli and Thermus thermophilus EF-Tu equal to 84% and 74%, respectively, while the identity with EF-1 alpha from the archaeon Sulfolobus solfataricus was equal to 32%.

The archaeal elongation factor 1alpha bound to GTP forms a ternary complex with eubacterial and eukaryal aminoacyl-tRNA

The archaeal Sulfolobus solfataricus elongation factor 1alpha (SsEF-1alpha) bound to GTP or to its analogue guanyl-5'-yl imido diphosphate [Gpp(NH)p] formed a ternary complex with either Escherichia coli Val-tRNAVal or Saccharomyces cerevisiae Phe-tRNAPhe as demonstrated by gel-shift and gel-filtration experiments. Evidence of such an interaction also came from the observation that SsEF-1alphaz.rad;Gpp(NH)p was able to display a protective effect against either the spontaneous deacylation or the digestion of aminoacyl-tRNA by RNase A. Protection against the deacylation of aminoacyl-tRNA allowed evaluatation of the affinity of SsEF-1alphaz. rad;Gpp(NH)p for both aminoacyl-tRNAs used. The K'd values of the ternary complex containing S. cerevisiae Phe-tRNAPhe or E. coli Val-tRNAVal were 0.3 microM and 4.4 microM, respectively. In both cases, the affinity of SsEF-1alphaz.rad;Gpp(NH)p for aminoacyl-tRNA was three orders of magnitude lower than that of the homologous eubacterial ternary complexes, but comparable with the affinity shown by the ternary complex involving eukaryal EF-1alpha [Negrutskii, B.S. & El'skaya, A.V. (1998) Prog. Nucleic Acids Res. 60, 47-77]. As already observed with eukaryal EF-1alpha, SsEF-1alpha in its GDP-bound form was also able to protect the ester bond of aminoacyl-tRNA, even though with a 10-fold lower efficiency compared with SsEF-1alphaz.rad;Gpp(NH)p. The overall results indicated that the archaeal elongation factor 1alpha shares several properties with eukaryal EF-1alpha but not with eubacterial EF-Tu.

A NAD(P)H oxidase isolated from the archaeon Sulfolobus solfataricus is not homologous with another NADH oxidase present in the same microorganism. Biochemical characterization of the enzyme and cloning of the encoding gene

A NAD(P)H oxidase has been isolated from the archaeon Sulfolobus solfataricus. The enzyme is a homodimer with M(r) 38,000 per subunit (SsNOX38) containing 1 FAD molecule/subunit. It oxidizes NADH and, less efficiently, NADPH with the formation of hydrogen peroxide. The enzyme was resistant against chemical and physical denaturating agents. The temperature for its half-denaturation was 93 and 75 degrees C in the absence or presence, respectively, of 8 M urea. The enzyme did not show any reductase activity. The SsNOX38 encoding gene was cloned and sequenced. It accounted for a product of 36.5 kDa. The translated amino acid sequence was made of 332 residues containing two putative betaalphabeta-fold regions, typical of NAD- and FAD-binding proteins. The primary structure of SsNOX38 did not show any homology with the N-terminal amino acid sequence of a NADH oxidase previously isolated from S. solfataricus (SsNOX35) (Masullo, M., Raimo, G., Dello Russo, A., Bocchini, V. and Bannister, J. V. (1996) Biotechnol. Appl. Biochem. 23, 47-54). Conversely, it showed 40% sequence identity with a putative thioredoxin reductase from Bacillus subtilis, but it did not contain cysteines, which are essential for the activity of the reductase.

A chimeric elongation factor containing the putative guanine nucleotide binding domain of archaeal EF-1 alpha and the M and C domains of eubacterial EF-Tu

A recombinant chimeric elongation factor containing the region of EF-1 alpha from Sulfolobus solfataricus harboring the site for GDP and GTP binding and GTP hydrolysis (SsG) and domains M and C of Escherichia coli EF-Tu (EcMC) was studied. SsG-EcMC did not sustain poly(Phe) synthesis in either S. solfataricus or E. coli assay system. This was probably due to the inability of the chimera to interact with aa-tRNA. The three-dimensional modeling of SsG-EcMC indicated only small structural differences compared to the Thermus aquaticus EF-Tu in the ternary complex with aa-tRNA and GppNHp, which did not account for the observed inability to interact with aa-tRNA. The addition of the nucleotide exchange factor SsEF-1 beta was not required for poly(Phe) synthesis since the chimera was already able to exchange [(3)H]GDP for GTP at very high rate even at 0 degrees C. Compared to that of SsEF-1 alpha, the affinity of the chimera for guanine nucleotides was increased and the k(cat) of the intrinsic GTPase was 2-fold higher. The heat stability of SsG-EcMC was 3 and 13 degrees C lower than that displayed by SsG and SsEF-1alpha, respectively, but 30 degrees C higher than that of EcEF-Tu. This pattern remained almost the same if the melting curves of the proteins being investigated were considered instead. The chimeric elongation factor was more thermophilic than SsG and SsEF-1 alpha up to 70 degrees C; at higher temperatures, inactivation occurred.

The A26G replacement in the consensus sequence A-X-X-X-X-G-K-[T,S] of the guanine nucleotide binding site activates the intrinsic GTPase of the elongation factor 2 from the archaeon Sulfolobus solfataricus

A recombinant form of the elongation factor 2 from the archaeon Sulfolobus solfataricus (SsEF-2), carrying the A26G substitution, has been produced and characterized. The amino acid replacement converted the guanine nucleotide binding consensus sequences A-X-X-X-X-G-K-[T,S] of the elongation factors EF-G or EF-2 into the corresponding G-X-X-X-X-G-K-[T,S] motif which is present in all the other GTP-binding proteins. The rate of poly(U)-directed poly(Phe) synthesis and the ribosome-dependent GTPase activity of A26GSsEF-2 were decreased compared to SsEF-2, thus indicating that the A26G replacement partially affected the function of SsEF-2 during translocation. In contrast, the A26G substitution enhanced the catalytic efficiency of the intrinsic SsEF-2 GTPase triggered by ethylene glycol [Raimo, G., Masullo, M., Scarano, G., & Bocchini, V. (1997) Biochimie 78, 832-837]. Surprisingly, A26GSsEF-2 was able to hydrolyse GTP even in the absence of ethylene glycol; furthermore, the alcohol increased the affinity for GTP without modifying the catalytic constant of A26GSsEF-2 GTPase. Compared to SsEF-2, the affinity of A26GSsEF-2 for [3H]GDP was significantly reduced. These findings suggest that A26 is a regulator of the biochemical functions of SsEF-2. The involvement of this alanine residue in the guanine nucleotide-binding pocket of EF-2 or EF-G is discussed.

The interaction between the archaeal elongation factor 1alpha and its nucleotide exchange factor 1beta

In Sulfolobus solfataricus the binding of the exchange factor 1beta (SsEF-1beta) to SsEF-1alpha-GDP displaces the nucleotide and the SsEF-1alpha-SsEF-1beta complex is formed. The complex itself is stable, but it dissociates upon the addition of GDP or Gpp(NH)p but not ATP. Since the rate of the formation of the SsEF-1alpha-SsEF-1beta complex is significatively slower than the rate of the nucleotide exchange catalyzed by SsEF-1beta it can be inferred that in vivo the GDP/GTP exchange reaction proceeds via an SsEF-1alpha-SsEF-1beta interaction without involving the formation of a stable binary complex as an intermediate.

Protein engineering on enzymes of the peptide elongation cycle in Sulfolobus solfataricus

The present article is a review of the work done on the elongation factors EF-1 alpha, EF-2 and EF-1 beta isolated from the hyperthermophilic archaeon Sulfolobus solfataricus. The molecular, physical and biochemical properties of the intact, truncated, mutant or chimeric forms are described and compared.

The effect of ribosome-inactivating proteins on the ribosome from the hyperthermophilic archaeon Sulfolobus solfataricus

Protein synthesis in the thermoacidophilic archaeon Sulfolobus solfataricus (Ss) was inhibited by polynucleotide:adenosine glycosylase activity of some type 1 ribosome-inactivating proteins (RIP). The target of RIP was S. solfataricus rRNA that was depurinated thus producing inactive ribosomes. The amount of RIP required to half-inactivated Ss-ribosomes was comparable to that needed for eubacterial ribosomes, but two orders of magnitude higher than that required for mammalian ribosomes. In addition, RIP treated Ss-ribosomes were also less efficient in stimulating the ribosome dependent GTPase activity of the S. solfataricus elongation factor 2 (SsEF-2) thus suggesting that the inhibition of protein synthesis was probably due to the lack of the interaction between depurinated Ss-ribosomes and SsEF-2. Since SsEF-2 protects Ss-ribosomes against RIP activity it can be hypothesised that also on Ss-ribosomes the sites of interaction for the translocation factor 2 and the RIP are topographically close.

Expression in Escherichia coli of the elongation factor 1beta gene and its nucleotide T160C mutant from the archaeon Sulfolobus solfataricus

The guanine nucleotide exchange factor EF-1beta gene from the thermoacidophilic archaeon Sulfolobus solfataricus (SsEF-1beta) was amplified by PCR and cloned into the pT7-7 expression vector. One of four selected clones harbored the T160C nucleotide substitution leading to the Y54H amino acid change in a hydrophobic region of SsEF-1beta, caused by a nucleotide misincorporation of the Taq DNA polymerase during PCR. The resulting plasmids were used to transform the Escherichia coli BL21(DE3)pLysE strain. Upon induction with isopropyl beta-d-thiogalactopyranoside about 1.4 mg of the recombinant SsEF-1beta (recSsEF-1beta) and Y54HSsEF-1beta were obtained from 1 liter of cell culture. recSsEF-1beta and Y54HSsEF-1beta were both able to catalyze the GDP/GTP exchange on SsEF-1alpha as observed with the wild-type SsEF-1beta. In addition, the heat inactivation profiles of recSsEF-1beta and Y54HSsEF-1beta were identical, being both half inactivated after 30 min treatment at 105 degrees C. These results suggest that Tyr 54 is not essential for the nucleotide exchange activity and is not involved in the thermostability of SsEF-1beta.

Iron superoxide dismutase from the archaeon Sulfolobus solfataricus: average hydrophobicity and amino acid weight are involved in the adaptation of proteins to extreme environments

The iron-superoxide dismutase in the thermoacidophilic archaeon Sulfolobus solfataricus has a homodimeric structure with a metal content of 0.7 atom of iron per subunit. The enzyme is insensitive to cyanide inhibition, sensitive to inactivation by H2O2 and is the most heat resistant SOD known so far being its half-life 2 h at 100 degrees C. Its primary structure was determined by a profitable combination of advanced mass spectrometry and automated sequence analysis of peptides obtained after cleavage of the purified protein. The enzyme subunit is composed of 210 amino acid residues accounting for a relative molecular mass of 24,112. It does not contain cysteine residues and has a high average of both hydrophobicity and amino acid weight. Vice versa, the hydrophobicity is lower in halophilic SODs. Therefore, it seems that the average hydrophobicity is involved in the adaptation of proteins to extreme environments. The multiple alignment of the primary structure of archaeal and thermophilic eubacterial SODs indicated that archaeal SODs evolved separately from the thermophilic eubacterial SODs and that halophiles originated from a gene different from that of thermophilic archaea.

Myofibrosarcoma of the breast: review of the literature on myofibroblastic tumors and criteria for defining myofibroblastic differentiation

A case of myofibrosarcoma of the breast is described. A 55-year-old woman presented with a small mammary nodule. A large recurrent lesions appeared a month later, and the patient died 11 months following initial presentation from diffuse pleuropulmonary metastases. Histologically, the primary tumor consisted mainly of spindled cells, arranged in fascicles and surrounded by varying quantities of dense hyaline collagen. The recurrent lesion had a more pleomorphic organization. In both lesions, there was positive immunostaining for vimentin, smooth-muscle actin, and fibronectin, and negative results for desmin, laminin, and type IV collagen. Electron microscopy revealed abundant rough endoplasmic reticulum, myofilaments with focal densities, and the fibronexus junctions and fibronectin fibrils characteristic of myofibroblasts. Given these cellular features and behavior, the tumor was interpreted as a malignant neoplasm showing myofibroblastic differentiation, i.e., a myofibrosarcoma. This case enlarges the group of myofibrosarcoma of breast, also with the demonstration of fibronexus and fibronectin fibrils. The paper emphasizes the criteria required for myofibroblastic differentiation and reviews lesions of the breast reported in the literature as myofibroblastic.

Properties of truncated forms of the elongation factor 1alpha from the archaeon Sulfolobus solfataricus

Two truncated forms of the Sulfolobus solfataricus elongation factor 1alpha (SsEF-1alpha), corresponding to the putative domains G+M, Ss(GM)EF-1alpha, and G, Ss(G)EF-1alpha, have been constructed by gene engineering, produced in Escherichia coli and purified. Neither truncated form was able to sustain poly(Phe) synthesis but they were able to bind guanine nucleotides with an affinity much higher with respect to that of the intact factor. However, the difference in the affinity for GDP and GTP became progressively reduced with the extent of the truncation. The values of kcat and Km for GTP of the intrinsic GTPase of SsEF-1alpha triggered by 3.6 M NaCl were not affected by the deletions. In contrast, both Ss(GM)EF-1alpha and Ss(G)EF-1alpha were less thermostable than the intact factor; the region of the factor most responsible for the loss of resistance against heat inactivation was the C-terminal domain. On the other hand the domain M was the regulator of the thermophilicity of SsEF-1alpha since only Ss(G)EF-1alpha showed a reduced thermophilicity. Remarkably, both Ss(GM)EF-1alpha and Ss(G)EF-1alpha were able to exchange [3H]GDP for GTP at a very high rate so that they were no more sensitive to the stimulatory effect of SsEF-1beta, which is the nucleotide exchange factor of SsEF-1alpha.

Archaeal elongation factor 1 beta is a dimer. Primary structure, molecular and biochemical properties

The elongation factor 1 beta (EF-1 beta), that in eukarya and archaea promotes the replacement of GDP by GTP on the elongation factor 1 alpha x GDP complex, was purified to homogeneity from the thermoacidophilic archaeon Sulfolobus solfataricus (SsEF-1 beta). Its primary structure was established by sequenced Edman degradation of the entire protein or its proteolytic peptides. The molecular weight of SsEF-1 beta was estimated as about 10000 or 20000 under denaturing or native conditions respectively; this finding suggests that the native protein exists as a dimer. The peptide chain of SsEF-1 beta is much shorter than that of its eukaryotic analogues and homology is found only at their C-terminal region; no homology exists between SsEF-1 beta and eubacterial EF-Ts. At 50 degrees C, at a concentration of SsEF-1 beta 5-fold higher than that of SsEF-1 alpha x [3H]GDP the rate of the exchange of [3H]GDP for GTP becomes about 160-fold faster. An analysis of the values of the energetic parameters indicates that in the presence of SsEF-1 beta the GDP/GTP exchange is entropically favoured. At 100 degrees C the half-life of SsEF-1 beta is about 4 h.

Expression in Escherichia coli of thermostable elongation factor 1 alpha from the archaeon Sulfolobus solfataricus

The elongation factor 1 alpha from the archaeon Sulfolobus solfataricus (SsEF-1 alpha) was expressed in Escherichia coli and purified. The SsEF-1 alpha gene was amplified by PCR and cloned in the Ndel site of the pT7-7 expression vector, under the control of the promoter of T7 RNA polymerase. Upon induction with isopropyl beta-D-thiogalactopyranoside, the recombinant SsEF-1 alpha (recSsEF-1 alpha) was purified from the E. coli S-100 extract by a two-step procedure. From 1 litre of cell culture, about 2 mg of purified recSsEF-1 alpha was obtained. The N-terminal sequence of the first 30 amino acid residues of recSsEF-1 alpha was identical with that translated from the nucleotide sequence of the corresponding gene, except for the initial residue, which in recSsEF-1 alpha was Ser instead of Met. The M(r) of recSsEF-1 alpha (determined by electrospray MS) was almost coincident with that of the naturally occurring SsEF-1 alpha (SsEF-1 alpha). The thermal-inactivation and thermophilicity profiles of SsEF-1 alpha and recSsEF-1 alpha were identical. Concerning the functional properties, recSsEF-1 alpha was able to support poly(Phe) synthesis in vitro, to bind GDP and GTP and to elicit an NaCl-dependent GTPase activity [Masullo, De Vendittis and Bocchini (1994) J. Biol. Chem. 269, 20376-20379] with the same efficiency as that displayed by SsEF-1 alpha.

Purification and characterization of NADH oxidase from the archaea Sulfolobus acidocaldarius and Sulfolobus solfataricus

The enzyme NADH oxidase (EC 1.6.99.3) has been isolated from the two thermoacidophilic archaea Sulfolobus acidocaldarius and Sulfolobus solfataricus and characterized. In both organisms the enzyme oxidizes specifically beta-NADH in the presence of molecular oxygen and requires the presence of a flavin cofactor, showing a high specificity for FAD. A stoicheiometric amount of hydrogen peroxide to NADH is formed as the end product of the reaction, indicating that both enzymes are two-electron donors. The purified enzymes exhibit quite different molecular properties. S. acidocaldarius NADH oxidase is a monomeric protein with an estimated molecular mass of about 27 kDa, whereas S. solfataricus NADH oxidase is a dimeric protein with a molecular mass of 35 kDa per subunit; S. solfataricus NADH oxidase is purified as an FAD-containing protein, whereas S. acidocaldarius NADH oxidase does not contain a flavin molecule. Furthermore, a comparison of the N-terminal amino acid sequence shows no similarities either between the two proteins or to any other NADH oxidases. Both enzymes are essentially thermophilic. In the temperature range 20-80 degrees C, the energy of activation is almost the same for both activities, suggesting that similar energetic parameters are required. Also both oxidases display a great stability to heat. The half-life of heat inactivation is about 180 min at 90 degrees C for S. acidocaldarius NADH oxidase and 77 min at 98 degrees C for the S. solfataricus enzyme. The activity of the two enzymes is inhibited by urea and guanidine and are regulated very differently by several organic solvents.

The site for GTP hydrolysis on the archaeal elongation factor 2 is unmasked by aliphatic alcohols

An appropriate mixture of ethylene glycol and BaCl2 enhanced the otherwise very low intrinsic GTPase activity of the elongation factor 2 isolated from the archaeon Sulfolobus solfataricus (SsEF-2). The enzymatic activity became up to 300-fold higher than that of the SsEF-2 GTPase measured in the absence of any stimulator, but remained 20-fold lower than that stimulated by ribosome. The stimulatory effect of ethylene glycol/Ba2+ was attributed to the increased affinity for GTP, probably related to a conformational change occurring in a hydrophobic region near the catalytic site.

Respiratory allergy to parietaria pollen in 348 subjects

We have revisited 348 records of allergic outpatients to Parietaria, ratio M/F 1:1 and mean age 29.46 +/- 12.49 yrs. 97 of them were skin positive to Parietaria only (A-group: M/F 37/60); 251 patients were skin positive also to other allergens (B-group: M/F 137/114). Mean age of A-group patients (35.41 +/- 12.91) was higher than B-group (27.16 +/- 11.54; p < 001). Dividing mono and polysensitized subjects by age decade, a different distribution was found between the two groups (p < 001): monosensitized patients showed an increasing number of subjects from the 3rd to the 4th decade and a decreasing trend in the following decades; polysensitized patients showed a prevalence in age < 20 yrs and a decreasing trend in the other decades. In B-group Gramineae were the most frequent allergens associated to Parietaria (84.8%) followed by Olea Europaea (41.1%), Dermatophagoides farinae (37.4%) and Dermatophagoides pteronyssinus (36.2%). Main symptoms were rhinoconjunctivitis (187 cases), rhinitis + asthma (141 cases) and bronchial asthma (20 cases). Comparing the clinical features of the two groups, we have found that monosensitized patients showed a female prevalence, a prevalence of rhinitis with late onset of symptoms while in patients suffering from isolated asthma the onset was early.

Tracheobronchial involvement in 84 cases of pulmonary tuberculosis

In suspected pulmonary tuberculosis (TB), tracheobronchial examination is required for patients with clinical and radiographic features consistent with tuberculosis disease but with negative sputum for Mycobacterium tuberculosis. We report the endoscopic findings of 84 patients who underwent fibreoptic bronchoscopy in recent years, and whose cultures of biological specimens grew M tuberculosis. Cough (86%) and fever (69%) were the most common symptoms, followed by sputum (67%), dyspnoea (30%) and haemoptysis (27%). Chest radiographic abnormalities were mostly localized (60%) with prevalence in the upper lobes; in two cases chest radiography was normal. Sixty two patients (74%) showed endoscopic abnormalities: 1) mucosal inflammation; 2) submucosal granulomas and polyps; and 3) stenoses. They were localized in 58% of patients and diffuse in 42%. Five patients were checked several times during the year following the diagnosis because of a high degree of tracheobronchial involvement. Only one subject recovered, whilst in the other four stenotic sequelae were found. Fibreoptic bronchoscopy confirmed its usefulness in the diagnosis of tuberculosis and in monitoring the course and the outcome of the bronchial tuberculosis involvement.

Studies on the polypeptide elongation factor 2 from Sulfolobus solfataricus. Interaction with guanosine nucleotides and GTPase activity stimulated by ribosomes

The elongation factor 2 from the thermoacidophilic archaeon Sulfolobus solfataricus (SsEF-2) binds [3H]GDP at 1:1 molar ratio. The bound [3H]GDP is displaced by GTP or its nonhydrolyzable analogue guanyl-5'-yl imidodiphosphate (Gpp(NH)p) but not by ATP, thus indicating that only the two guanosine nucleotides compete for the same binding site. The affinity of SsEF-2 for [3H]GDP is higher than that for GTP and Gpp(NH)p. On the contrary, in the presence of ribosomes the affinity of SsEF-2 for GDP is lower than that for Gpp(NH)p. SsEF-2 is endowed with an intrinsic hardly detectable GTPase activity that is stimulated by ribosomes up to 2000-fold. The ribosome-stimulated SsEF-2 GTPase (GTPaser) reaches a maximum at pH 7.8 and is not affected by ATP but is competitively inhibited by either GDP or Gpp(NH)p. Both Km for [gamma-32P]GTP and kcat of GTPaser increase with increasing temperature, and the highest catalytic efficiency is reached at 80 degrees C. The ADP-ribosylation of SsEF-2 does not significantly affect either the binding of GDP and GTP or the kinetics of the GTPaser. A hypothesis on the stimulation by ribosome of SsEF-2 GTPase is proposed.

Glyceraldehyde-3-phosphate dehydrogenase in the hyperthermophilic archaeon Sulfolobus solfataricus: characterization and significance in glucose metabolism

Glyceraldehyde-3-phosphate dehydrogenase in the archaeon Sulfolobus solfataricus (SsGAPD) has been purified 232 fold with an overall recovery of about 25%. The enzyme is a homomeric tetramer with an M(r) of 41 kDa/subunit. It utilizes either NAD+ or NADP+ as coenzyme but its affinity for the latter is about 50 fold higher. SsGAPD activity is maximum at 87 degrees C. In the range 45-87 degrees C the Arrhenius plot is linear and the activation energy is 55 kJ/mol. The enzyme is thermostable, with a half-life of 45 min at 87 degrees C. The primary structure of SsGAPD shows 35% identity with that of other archaeal GAPDs. Its N-domain shows sequence motifs typical of the dinucleotide binding proteins while the catalytic C-terminal region contains a cysteine residue (C140), required for catalysis, that is conserved in all the archaeal, eukaryal and bacterial GAPDs. These remarks suggest that archaeal GAPDs show a convergent molecular evolution to the eukaryal and eubacterial enzymes in the catalytic region.

Archaebacterial elongation factor 1 alpha carries the catalytic site for GTP hydrolysis

The elongation factor 1 alpha from the archaebacterium Sulfolobus solfataricus (aEF-1 alpha) possesses an intrinsic GTPase activity that is triggered by NaCl up to 5.2 M and requires the presence of at least 1 mM MgCl2 or MnCl2. Chloride salts of other monovalent cations are inefficient, whereas other sodium salts are much less efficient or not efficient at all as compared with NaCl. This aEF-1 alpha GTPase (GTPaseNa) reaches a maximum in a broad pH range and is not affected by other nucleoside triphosphates but is competitively inhibited by GDP. The turnover of GTPaseNa is rate limited by the breakdown of GTP. The Km for GTP is in the range of 2.2-9.3 microM, depending on the NaCl concentration and temperature. The highest catalytic efficiency is reached at 87 degrees C, which is the optimum temperature for growth of S. solfataricus. The energetic parameters of GTPaseNa are similar to those reported in the literature for the GTPase of Escherichia coli elongation factor Tu (EF-Tu) triggered by 2 M KCl, thus suggesting that the GTPase activity supported by either EF-Tu or aEF-1 alpha undergoes a similar mechanism of activation by salt at high concentration. A molecular mechanism for this activation is proposed.

Cloning and sequencing of the gene encoding thermostable elongation factor 2 in Sulfolobus solfataricus

The gene (aEF-2) coding for the translation elongation factor 2 (aEF-2) in the thermoacidophilic archaebacterium, Sulfolobus solfataricus, has been cloned and sequenced. The deduced primary structure of aEF-2 is composed of 735 amino acids (aa), excluding the Met start residue. There are no Cys residues and the calculated M(r) is 81,699. In the coding region of aEF-2, the high A + T content greatly influences the codon usage. From the alignment of the primary structure of aEF-2 with that of the analogous factors from the three kingdoms, aa identities were derived. The greatest identity (82%) was found with EF-2 from Sulfolobus acidocaldarius; lower values were observed with other archaebacterial EF-2 (45-47%), eukaryotic EF-2 (38-40%) and with the functional eubacterial analogue EF-G (28-31%). aEF-2 possesses the consensus sequences required for a GTP-binding protein and the four regions which are supposed to be involved in the functional regulation of EF-2/EF-G. These data should have phylogenetic implications.

Resistance of archaebacterial aEF-1 alpha.GDP against denaturation by heat and urea

The elongation factor aEF-1 alpha, isolated as aEF-1 alpha.GDP from the thermoacidophilic archaebacterium Sulfolobus solfataricus, exchanges GDP for [3H]GDP at a rate which reaches a maximum at 95 degrees C. The rate constants at different temperatures of the heat inactivation of aEF-1 alpha.GDP are considerably lower compared to those referred to Escherichia coli EF-Tu.GDP. The Tm values determined for both aEF-1 alpha.GDP and EF-Tu.GDP are 97 and 53 degrees C, respectively. The addition of GDP during the heat treatment protects significantly EF-Tu.GDP but only slightly aEF-1 alpha.GDP. The ability of aEF-1 alpha.GDP to exchange GDP for [3H]GDP is impaired at 70 degrees C by urea at concentrations which are greater compared to those required to inactivate E. coli EF-Tu.GDP at 45 degrees C; apparently both factors are not protected by GDP against inactivation by urea.

Allergic skin tests and respiratory diseases in 1612 subjects

In 1985-90, 1612 subjects were submitted to allergic tests for respiratory diseases. In a retrospective survey we have evaluated clinical features, symptoms, diagnostic procedure and allergic tests of skin positives and skin negatives. Prick tests were supplemented by intradermal reaction and RAST under guideline of history. Allergens examined were Gramineae, Parietaria, Olea, house dust, Dermatophagoides farinae and pteronyssinus. 80% of patients were found positive to one or more allergens; their average age (30.1 +/- 13.7) was found lower (p < 0.001) and allergic family history prevalence higher (p < 0.01) than skin negatives. Skin positives prevalence was statistically significant under 50 yrs and skin negatives one over 50 yrs. Asthma or rhinitis only were prevalent among skin negatives while associated symptoms (asthma + rhinitis and/or conjunctivitis) were prevalent among skin positives. Considering skin results pollens were found positive in 34%, inhalants in 24% and pollens + inhalants in 42% of subjects. Gramineae were found positive in 57.8% of subjects, Parietaria in 39.8%, olea in 28.8%, Dermatophagoides farinae in 53.3%, house dust in 52.1% and Dermatophagoides pteronyssinus in 48.2%. Prick test showed a high sensitiveness in detecting pollens sensitization while intradermal reactions were often necessary in sensitization to inhalants; for the diagnosis RAST contribution was negligible.

Properties of the purified elongation factor 2 in the thermoacidophilic archaebacterium Sulfolobus solfataricus

The elongation factor 2 (aEF-2) has been purified to homogeneity from the extreme thermoacidophilic archaebacterium Sulfolobus solfataricus. It is the only target protein which is ADP-ribosylated by diphtheria toxin in presence of NAD and this modification abolishes its property to support poly(Phe) synthesis in vitro. The factor is constituted by a single polypeptide chain with a relative molecular mass of 78,000 and an isoelectric point of 5.9. aEF-2 is resistant to heat denaturation as shown by the fact that its capability to be ADP-ribosylated was only 10% reduced after 4 h treatment at 80 degrees C. Its amino acid composition does not reveal significant differences with that of analogous factors in other sources; nevertheless, the deviation function indicates that aEF-2 is related to Sulfolobus acidocaldarius and eukaryotes EF-2 more than to eubacterial EF-G or other archaebacterial EF-2.

Molecular, functional and structural properties of an archaebacterial elongation factor 2

The elongation factor 2 (aEF-2) from the extreme thermo-acidophilic archaebacterium Sulfolobus solfataricus, is the only cytosolic target protein which is ADP-ribosylated by diphtheria toxin in presence of NAD. Once ADP-ribosylated, aEF-2 is no longer able to sustain poly(Phe) synthesis in vitro. aEF-2 displays a great thermoresistance: at the growth temperature of the archaebacterium, 87 degrees C, its half-life is 3 h. The amino acid sequence of the N-terminal region of aEF-2 has been determined up to residue 22. In the first 15 positions such a sequence is identical to that of EF-2 from Sulfolobus acidocaldarius and very similar to that of EF-2 from other archaebacteria or eukaryotes. The same is true for the primary structure of the peptide containing the ADP-ribosylation site. The fact that the primary structure of EF-2 at the ADP-ribosylation site is highly conserved ensures either the correct recognition of the histidine residue by the enzymes involved in its modification to diphthamide, or the proper interaction with the diphtheria toxin.

Allergic skin reactivity in 232 patients over 50 years

We examined two hundred and thirty-two out-patients, ranging in age from 50 to 75 yrs. All patients were submitted to skin-tests: prick and, if it was necessary, intradermal reactions and/or RAST. Allergens employed were Gramineae, Parietaria, Olea, dermatophagoides Farinae, dermatophagoides Pteronyssinus, house dust, cat and dog skin scales. One hundred and twenty-eight subjects had positive responses to one or more aeroallergens. Asthma was the most frequent condition both in skin-positives and in skin-negatives. For 58% of skin-positives and 51% of skin-negatives the symptoms' onset was more than 10 yrs before our check. In 58.6% of patients we found positive reaction to dermatophagoides Farinae, in 51.5% to house dust, in 47.6% to dermatophagoides Pteronyssinus, in 34.3% to Gramineae, in 28.9% to parietaria and in 14.8% to olea. Fifty-four skin-positives subjects carried out lung function tests; in twenty-eight of them we found a bronchial obstruction. In more than 50% of the subjects, which had shown a reactivity to aeroallergens, we prescribed a specific hyposensitization. These data suggest that skin tests results in elderly patients can have a relevant role in preventive and pharmacological treatment, improving life quality.

Properties of the elongation factor 1 alpha in the thermoacidophilic archaebacterium Sulfolobus solfataricus

The elongation factor 1 alpha (aEF-1 alpha) was purified to homogeneity from the thermoacidophilic archaebacterium Sulfolobus solfataricus by chromatographic procedures utilising DEAE-Sepharose, hydroxyapatite and FPLC on Mono S. The purified protein binds [3H]GDP at a 1:1 molar ratio and it is essential for poly(Phe) synthesis in vitro; it also binds GTP but not ATP. These findings indicate that aEF-1 alpha is the counterpart of the eubacterial elongation factor Tu (EF-Tu). Purified aEF-1 alpha is a monomeric protein with a relative molecular mass of 49,000 as determined by SDS/PAGE and by gel filtration on Sephadex G-100; its isoelectric point is 9.1. The overall amino acid composition did not reveal significant differences when compared with the amino acid composition of eubacterial EF-Tu from either Escherichia coli or Thermus thermophilus, of eukaryotic EF-1 alpha from Artemia salina or of archaebacterial EF-1 alpha from Methanococcus vannielii. The close similarities between the average hydrophobicity and the numbers of hydrogen-bond-forming or non-helix-forming residues suggest that common structural features exist among the factors compared. aEF-1 alpha shows remarkable thermophilic properties, as demonstrated by the rate of [3H]GDP binding which increases with temperature, reaching a maximum at 95 degrees C; it is also quite heat-resistant, since after a 6-h exposure at 60 degrees C and 87 degrees C the residual [3H]GDP-binding ability was still 90% and 54% of the control, respectively. The affinity of aEF-1 alpha for GDP and GTP was also evaluated. At 80 degrees C Ka' for GDP was about 30-fold higher than Ka' for GTP; at the same temperature Kd' for GDP was 1.7 microM and Kd' for GTP was 50 microM; these values were 300-fold and 100-fold higher, respectively, than those reported for E. coli EF-Tu at 30 degrees C; compared to the values at 0 degree C of EF-Tu from E. coli and T. thermophilus or EF-1 alpha from A. salina, pig liver and calf brain, smaller differences were observed with eukaryotic factors.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of propan-2-ol on enzymic and structural properties of elongation factor G

Elongation factor G (EF-G) can support a GTPase activity in vitro even in the absence of ribosomes when propan-2-ol is present [GTPasep; De Vendittis, Masullo & Bocchini (1986) J. Biol. Chem. 261, 4445-4450]. In the present work the GTPasep activity of EF-G was further studied by investigating (i) the effect of ionic environment on GTPasep and (ii) the influence of propan-2-ol on the molecular structure of EF-G as determined by fluorescence and c.d. measurements. In the presence of 1-300 mM univalent cations (M+) alone, no detectable GTPasep activity was measured; however, in the presence of 1 mM-Mg2+ a considerable stimulation was observed at 40 mM-Li+ or 75 mM-NH4+. Among bivalent cations (M2+), 1 mM-Sr2+, 2-5 mM-Ca2+ and 1 mM-Ba2+ were the most effective, but, in the presence of 75 mM-NH4+, Mg2+ and Mn2+ became the most efficient, whereas the stimulation by other M2+ species was considerably decreased. C.d. measurements showed that the alcohol increased the mean molar residue ellipticity of EF-G at 285 nm, but not at 220 nm. As estimated from fluorescence measurements, in the presence of 20% (v/v) propan-2-ol the value of the dissociation constant of the complex formed between EF-G and 8-anilino-1-naphthalene-sulphonate decreased from 8 to 5 microM; similarly, the number of binding sites on EF-G for the fluorescent probe decreased from 13 to 6. Finally, the alcohol enhanced the quenching of the intrinsic fluorescence of EF-G caused by either acrylamide or KI. The data support the hypothesis that propan-2-ol induces moderate conformational changes of EF-G that make the catalytic centre accessible to the substrate even in the absence of ribosomes. Kinetics of GTPasep studied at different temperatures did not reveal additional structural changes of EF-G occurring with time or temperature.

The elongation factor G carries a catalytic site for GTP hydrolysis, which is revealed by using 2-propanol in the absence of ribosomes

In the absence of ribosomal particles, elongation factor G (EF-G) promotes very little GTP hydrolysis. After the addition of some aliphatic alcohols to EF-G, the rate of nucleotide cleavage was significantly increased and GTPase activity was easily detectable. The highest stimulation, nearly 16-fold, occurred with 2-propanol at a 20% (v/v) concentration. The reaction showed the characteristics of an enzymatic catalysis, but the rate was three orders of magnitude lower than that of the ribosome-dependent EF-G GTPase activity. Striking similarities between the two activities indicated that the catalysis stimulated by the alcohol was due to EF-G itself. We found that EF-G GTPase activity in the presence of 2-propanol displayed an absolute specificity for GTP as in the presence of ribosomes; the two activities copurified to a constant ratio and exhibited coincident chromatographic and electrophoretic patterns; the temperature for the half-inactivation of EF-G was 59.3 degrees C for both GTPase systems, as well as the kinetic constant for the thermal inactivation process which was found to be 0.05 min-1; and the Km for the GTP in the presence of 2-propanol (59 microM) was similar to that found in the presence of ribosomes. These results indicate that the EF-G molecule carries a catalytic site for GTP hydrolysis, which in the absence of ribosomal particles is activated by an appropriate alcohol/water surrounding medium.