Effect of glycosylation on the stability of alpha1-antitrypsin toward urea denaturation and thermal deactivation

The effects of glycosylation on the stability of human alpha1-antitrypsin were investigated. The transition midpoints in urea-induced equilibrium unfolding of a non-glycosylated recombinant, a yeast version of glycosylated, and human plasma alpha1-antitrypsin were 1.8 M, 2.2 M, and 2.5 M at 25 degrees C, respectively. Kinetic analyses of unfolding and refolding revealed that glycosylation retarded the unfolding without affecting the refolding rate significantly, suggesting that the stability increase is due to the stabilization of the native state as opposed to the destabilization of the unfolded state. In thermal deactivation, which is a heat-induced aggregation process, the unglycosylated recombinant alpha1-antitrypsin was deactivated most easily, which was followed in order by the yeast, and the plasma form. The results indicate that glycosylation confers the increase in stability of alpha1-antitrypsin, and that the oligomannose sugars present on the yeast form produce a less stable molecule than the complex type sugars on the plasma form. It appears that the effect of glycosylation on the enhancement of thermal resistance is exerted through the increase in conformational stability. However, a stable recombinant variant (Phe 51 --> Cys) that showed the same conformational stability as the plasma form was less resistant to thermal denaturation than the plasma alpha1-antitrypsin. The results suggest that the existence of carbohydrate moiety per se as well as the conformational stability contribute to the kinetic stability of alpha1-antitrypsin toward aggregation.

Side-chain specificity at three temperature-sensitive folding mutation sites of P22 tailspike protein

The phage P22 tailspike protein is one of the few proteins for which both in vivo and in vitro folding pathways have been thoroughly characterized. Many temperature-sensitive folding (tsf) mutations that cause the mutant tailspike polypeptides not to be folded at high restrictive temperatures have been identified. One-third of the tsf mutation sites are located in one domain called the dorsal fin domain (residues 197-259), which protrudes on the solvent-exposed side of the main beta helix. In the present study, we introduced various amino acid substitutions at three tsf mutation sites (residue numbers 235, 238, and 244) in this domain to elucidate the mechanism of these tsf mutations in detail. The side-chain specificity at these tsf sites, together with structural examination in the tertiary fold, strongly suggests that destabilization of folding intermediates by loss of specific interactions is likely to be the major cause of the tsf defect in the dorsal fin domain.

Folding and stability of the Z and S(iiyama) genetic variants of human alpha1-antitrypsin

Z (Glu342 --> Lys) and S(iiyama) (Ser53 --> Phe) genetic variations of human alpha1-antitrypsin (alpha1-AT) cause a secretion blockage in the hepatocytes, leading to alpha1-AT deficiency in the plasma. Using in vitro folding analysis, we have shown previously that these mutations interfere with the proper folding of polypeptides. To understand the fundamental cause for the secretion defect of the Z and S(iiyama) variants of alpha1-AT, we investigated in vivo folding and stability of these variant alpha1-AT using the secretion system of yeast Saccharomyces cerevisiae. Various thermostable mutations suppressing the folding block of the Z variant in vitro corrected the secretion defect as well as the intracellular degradation in the yeast secretion system. Significantly, the extent of suppression in the secretion defect of Z protein was proportional to the extent of suppression in the folding defect, assuring that the in vivo defect associated with the Z variant is primarily derived from the folding block. In contrast, the folding and secretion efficiency of S(iiyama) was not much improved by the same mutations. In addition, none of the rarely secreted S(iiyama) alpha1-AT carrying the stabilizing mutations for the wild type and Z variant were active. It appears that the major defect in S(iiyama) variant is the loss of stability in contrast to the kinetic block of folding in the Z variant.

The native strains in the hydrophobic core and flexible reactive loop of a serine protease inhibitor: crystal structure of an uncleaved alpha1-antitrypsin at 2.7 A

BACKGROUND

The protein alpha1-antitrypsin is a prototype member of the serpin (serine protease inhibitor) family and is known to inhibit the activity of neutrophil elastase in the lower respiratory tract. Members of this family undergo a large structural rearrangement upon binding to a target protease, involving cleavage of the reactive-site loop. This loop is then inserted into the main body of the enzyme following the opening of a central beta sheet, leading to stabilization of the structure. Random mutageneses of alpha1-antitrypsin identified various mutations that stabilize the native structure and retard the insertion of the reactive-site loop. Structural studies of these mutations may reveal the mechanism of the conformational change.

RESULTS

We have determined the three-dimensional structure of an uncleaved alpha1-antitrypsin with seven such stabilizing mutations (hepta alpha1-antitrypsin) at 2.7 A resolution. From the comparison of the structure with other serpin structures, we found that hepta alpha1-antitrypsin is stabilized due to the release of various strains that exist in native wild type alpha1-antitrypsin, including unfavorable hydrophobic interactions in the central hydrophobic core. The reactive-site loop of hepta alpha1-antitrypsin is an extended strand, different from that of the previously determined structure of another uncleaved alpha1-antitrypsin, and indicates the inherent flexibility of the loop.

CONCLUSIONS

The present structural study suggests that the uncleaved alpha1-antitrypsin has many folding defects which can be improved by mutations. These folding defects seem to be utilized in a coordinated fashion in the regulation of the conformational switch of alpha1-antitrypsin. Some of the defects, represented by the Phe51 region and possibly the Met374 and the Thr59 regions, are part of the sheet-opening mechanism.

Folding pathway of human alpha 1-antitrypsin: characterization of an intermediate that is active but prone to aggregation

The folding-unfolding kinetics of human alpha 1-antitrypsin (alpha 1-AT) were examined by monitoring intrinsic Trp fluorescence and extrinsic ANS fluorescence. While the unfolding of alpha 1-AT followed a single exponential phase, refolding exhibited three exponential phases. The fast phase (tau 1r < 40 sec). which was independent of urea concentration, appears to be hydrophobic collapse that may be limited by cis-trans isomerization of prolyl residue. The medium phase (tau 2s = 200 sec) yielded an intermediate (IN), which is capable of elastase binding. The slowest (tau 3r = 1000 sec) phase completes refolding to the native protein, which intersects with the unfolding kinetics at the same urea concentration (1.9 M) as the equilibrium midpoint. Concentration-dependence of the amplitude of major refolding phases indicated that IN is prone to kinetic competition between the on-pathway to native protein and aggregation.

Transcervical flexible endoscopy for first trimester embryonic/fetal evaluation

OBJECTIVE

The aim of the study was to investigate the efficacy of flexible embryofetoscopy for visualization of the first trimester human embryo and fetus.

METHOD

Twelve pregnant women scheduled for legal termination of pregnancy at 6-12 weeks' gestation were included in the study. A flexible fiber optic endoscope with an eyepiece connected to a monitor was used. The sterile endoscope was passed transcervically under ultrasound guidance through the chorion into the chorionic cavity. Embryos/fetuses were observed directly through the intact amniotic membrane.

RESULT

Successful embryofetoscopies with clear visualization of the embryo or fetus were accomplished in 50% of cases. There were no procedure-related complications.

CONCLUSION

Preliminary experience employing transcervical flexible embryofetoscopy for direct visualization of the first trimester human embryo and fetus suggest that this technique may be used for the early identification of congenital anomalies suspected by ultrasound and is expected to offer opportunities for embryo/fetal tissue sampling as well as for gene and cell therapies.

High-level secretion of human alpha 1-antitrypsin from Saccharomyces cerevisiae using inulinase signal sequence

The use of a proper signal sequence is one of the major determinants for the efficient secretion of heterologous proteins from yeast. The signal sequence derived from inulinase (INU1A) of Kluyveromyces marxianus was evaluated in directing the secretion of a human glycoprotein, alpha 1-antitrypsin (alpha 1-AT), from Saccharomyces cerevisiae. A yeast expression vector for alpha 1-AT was constructed by placing the coding sequence of human alpha 1-AT fused with the INU1A signal sequence downstream of the GAL10 promoter. S. cerevisiae transformants harboring the expression vector secreted about 70% of the total alpha 1-AT synthesized into the culture media. The intracellularly retained form of alpha 1-AT was mostly unglycosylated, whereas the secreted protein had high mannose-type glycosylation. The fed-batch cultivation of the recombinant yeast achieved a high-cell density, leading to the secretion of biologically active alpha 1-AT up to 75 mg l-1. The secreted protein was purified and subjected to N-terminal sequencing, which confirmed that the secreted alpha 1-AT was processed correctly at the Kex2 cleavage site as expected from the sequence of INU1A signal peptide. The results suggest that the inulinase signal sequence is useful for the high-level secretion of relatively large glycoproteins, such as human alpha 1-AT, from S. cerevisiae.

Crystal structure of an uncleaved alpha 1-antitrypsin reveals the conformation of its inhibitory reactive loop

The crystal structure of a recombinant human alpha 1-antitrypsin, in the uncleaved and uncomplexed state, has been determined by X-ray crystallographic methods and refined to an R-factor of 18.4% for 8.0-3.46 A data with good stereochemistry. This structure provides the first view at the inhibitory loop and the central beta-sheet A of the uncleaved alpha 1-antitrypsin. The reactive loop takes a distorted helical conformation and no pre-insertion of two residues in the reactive loop into the beta-sheet A is observed. The present structure is largely in agreement with the model predicted by Engh, Wright, and Huber [Prot. Eng. 3 (1990) 469-477].

Purification and characterization of alpha 1-antitrypsin secreted by recombinant yeast Saccharomyces diastaticus

The secreted human alpha 1-antitrypsin (alpha 1AT) produced by yeast was purified from the culture medium by ultrafiltration, ammonium sulfate fractionation (60-75% saturation), protamine sulfate treatment, and ion-exchange chromatography. Molecular mass of the purified alpha 1AT was 52 kDa, which is similar to that of human plasma alpha 1AT. Yeast-produced alpha 1AT was fully functional as an inhibitor compared with the plasma form. Unlike plasma alpha 1AT, however, treatment of the yeast-produced alpha 1AT with endoglycosidase H decreased the molecular mass to that of recombinant alpha 1AT produced in Escherichia coli, indicating the high-mannose type N-linked glycosylation of the secreted alpha 1AT. Glycosylation in yeast cells enhanced kinetic stability of alpha 1AT towards heat deactivation.

Hernia uteri (correction of: uterus) inguinale associated with unilateral renal agenesis

We report a patient with a rudimentary uterine horn, fallopian tube and ovary in an inguinal hernia. Associated with this abnormality the patient had ipsilateral renal agenesis and a unicornuate uterus.

Contribution of individual side-chains to the stability of BPTI examined by alanine-scanning mutagenesis

Bovine pancreatic trypsin inhibitor (BPTI) serves as an important model system for the examination of almost all aspects of protein structure. Systematic studies of the effects of mutation on the thermodynamic stability of BPTI, however, have been limited by the extreme stability of the protein. A derivative of BPTI containing only the 5-55 disulfide bond, termed [5-55]Ala, has been shown previously to fold into a structure very similar to that of native BPTI and to be a functional trypsin inhibitor. [5-55]Ala undergoes a reversible thermal unfolding transition with a melting temperature of 39 degrees C, and is therefore well suited for stability studies. Using an alanine-scanning mutagenesis approach, we have examined the contribution to stability of each side-chain in the [5-55]Ala derivative of BPTI. These studies demonstrate the importance of the two hydrophobic cores composed largely of clusters of aromatic residues, as well as the internal hydrogen-bonding network, in stabilizing BPTI. Overall, there is a strong relationship between change in buried surface area and stability for both polar and hydrophobic residues, with proportionality constants of 50 and 20 cal/A2, respectively. None of the alanine substitutions substantially stabilized [5-55]Ala. Nonetheless, approximately 60% (28/46) of the alanine mutants were destabilized by less than 10 degrees C, suggesting that a form of BPTI with up to half of its residues being alanine could fold into a stable structure resembling the native one.

Mutations that stabilize folding intermediates of phage P22 tailspike protein: folding in vivo and in vitro, stability, and structural context

The folding of the trimeric phage P22 tailspike protein is affected by single amino acid substitutions designated temperature-sensitive folding (tsf) mutations. Their phenotypes are alleviated by two repeatedly isolated global suppressor (su) mutations (su V331A and su A334V) and by two additional substitutions (su V331G and su A334I), accessible through site-directed mutagenesis. We investigated the influence of the suppressor mutations on tailspike refolding in vitro, on its maturation at high expression levels in vivo, and on the rates of thermal unfolding of the native protein. All su mutations improved the folding efficiency in vitro and in vivo, but the relative effects of substitutions at position 334 were more pronounced in vivo, whereas the 331 substitutions were more effective in vitro. V331G caused the strongest increase in refolding yields of any single mutation, and was as effective as the V331A/A334V double mutation, where the two single mutations exhibited an additive effect. Both V331A and V331G retarded thermal denaturation, while A334V did not affect, and A334I accelerated unfolding. A334I is the first mutation found to affect the folding of the tailspike and the thermal stability of the native protein in opposite directions. The observed effects can be rationalized on the basis of the recently determined crystal structure of an N-terminally shortened tailspike. As the backbone dihedral angles of Val331 (phi = -119 degrees, psi = -142 degrees) are unusual for non-glycine residues, V331G and V331A may remove steric strain and thereby stabilize folding intermediates and the native protein. The beta-branched side-chains of Val and Ile substituted for Ala334 in the interior of the protein may improve a hydrophobic stack of residues in the large parallel beta-helix. This is likely important in loosely structured early folding intermediates, but not in the very rigid native structure, where the side-chain of Ile can hardly be accommodated.

The Z type variation of human alpha 1-antitrypsin causes a protein folding defect

Emphysema is often associated with the Z type mutation of alpha 1-antitrypsin, which causes aggregation of the molecule in the liver and consequent plasma deficiency. The aggregation appears to be due to loop-sheet polymerization, although why the mutant protein polymerizes in vivo is unclear. Here we show that, unlike wild type antitrypsin, which folds in minutes, the folding of Z type alpha 1-antitrypsin is extremely slow. Once folded, however, the native Z protein shows substantial stability towards urea and incubation at 37 degrees C. The folding defect in Z antitrypsin leads to accumulation of an intermediate and it is the intermediate rather than the native protein which has a high tendency to aggregate.

A thermostable mutation located at the hydrophobic core of alpha 1-antitrypsin suppresses the folding defect of the Z-type variant

A thermostable mutation, F51L, at the hydrophobic core of human alpha 1-antitrypsin (alpha 1AT) increased the conformational stability of the molecule by decreasing the unfolding rate significantly without altering the refolding rate. The mutation specifically influenced the transition between the native state and a compact intermediate, which retained approximately 70% of the far-UV CD signal, but which had most of the fluorescence signal already dequenched. The mutant alpha 1AT protein was more resistant than the wild-type protein to the insertion of the tetradecapeptide mimicking the sequence of the reactive center loop, indicating that the mutation increases the closing of the central beta-sheet, the A-sheet, in the native state. The F51L mutation enhanced the folding efficiency of the Z-type (E342K) genetic variation, which causes aggregation of the molecule in the liver. It has been shown previously that the aggregation of the Z protein occurs via loop-sheet polymerization, in which the reactive center loop of one molecule is inserted into the opening of the A-sheet of another molecule. Our results strongly suggest that the hydrophobic core of alpha 1AT regulates the opening-closing of the A-sheet and that certain genetic variations that cause opening of the A-sheet can be corrected by inserting an additional stable mutation into the hydrophobic core.

Refolding of alpha 1-antitrypsin expressed as inclusion bodies in Escherichia coli: characterization of aggregation

Recombinant alpha 1-antitrypsin (alpha 1AT) produced as inclusion bodies in Escherichia coli was purified via several steps including solubilization of the inclusion bodies in 8 M urea and refolding by direct dilution of denaturant, followed by ion-exchange chromatography. The purified recombinant alpha 1AT has an activity comparable to human plasma alpha 1AT. During refolding, prolonged incubation of the alpha 1AT polypeptides at intermediate urea concentration favored production of inactive but soluble aggregates, which could regain activity after denaturation and renaturation. Nondenaturing polyacrylamide gel electrophoresis of the aggregates revealed the existence of dimers and higher oligomers. Immunological approach to characterize conformation showed that the oligomers were distinct from the native, the cleaved, or the denatured form, but was similar to the polymers induced from the native structure in mild denaturing condition. These results suggest that the oligomers are formed through specific interactions between aggregation-competent species which are stabilized at intermediate denaturant concentration.

Cross-talk between N-methyl-D-aspartate and adrenergic neurotransmission in the regulation of hypothalamic GnRH gene expression

Although it has been known that activation of N-methyl-D-aspartate (NMDA) receptor effectively stimulates GnRH biosynthesis and release from the rat hypothalamus, no evidence that NMDA receptors exist in GnRH neurons is yet available. It is then presumed that the action of NMDA on GnRH neurons may be indirectly mediated through interneurons, such as catecholamines. The present study is designed to investigate whether the effect of NMDA on GnRH gene expression is mediated by adrenergic neuronal system. Adrenergic receptor antagonists were administered 30 min prior to NMDA administration to immature male rats and then animals sacrificed 60 min after NMDA administration. GnRH mRNA levels were determined by Northern blot analysis using a GnRH RNA probe. Inhibition of either alpha 1 adrenergic receptor with prazosin or beta adrenergic receptor with propranolol did not cause any change in the basal GnRH mRNA levels but reduced NMDA-induced GnRH mRNA levels. However, inhibition of alpha 2 adrenergic receptor with yohimbine increased GnRH mRNA levels but did not affect NMDA-induced GnRH mRNA levels. These findings suggest that the effect of NMDA on GnRH gene expression is mediated through adrenergic neurotransmission.

[Seroprevalence of human immunodeficiency virus infection in Guinea-Bissau, west Africa]

The seroprevalence of human immunodeficiency virus (HIV) infection in Guinea-Bissau, West Africa, was determined by enzyme-linked immunosorbent assay (ELISA). From January 1987 to February 1993, 590 patients from the outpatient and inpatient departments of Regional Hospital at Canchungo, Cacheu, Guinea-Bissau were studied. The overall seropositive rate was 16%. Patients in the age between 25 and 54 accounted for 78% of HIV-positive cases. The seropositive rate according to the diagnosis was: 6% in pregnant women, 40% in patients with gonorrhea/syphilis, 14% in patients with vaginitis and 22% in patients with active pulmonary tuberculosis. The seropositivity for HIV-1/2 in the pregnant women might reflect the seroprevalence in general population of Guinea-Bissau. Accordingly, the estimated population infected by HIV would be sixty thousands in Guinea-Bissau. Both sexually-transmitted diseases and tuberculosis were the risk factors for HIV infection. This study shows that HIV infection is a critical problem of public health in Guinea-Bissau. Strategies to prevent the seeding of HIV are of great importance. Moreover, the members of medical mission from our country must keep alert for preventing HIV infection.

Single amino acid substitutions of alpha 1-antitrypsin that confer enhancement in thermal stability

A recombinant alpha 1-antitrypsin variant which increased thermal stability was obtained from random mutagenesis followed by screening. The clone was identified as having a single mutation of Phe51-->Cys. Heat deactivation of purified recombinant alpha 1-antitrypsin produced in Escherichia coli revealed that the mutation slowed down the deactivation rate 10-fold at 57 degrees C, increasing thermal stability of recombinant protein to almost that of natural glycosylated plasma form. The mutant protein also exhibited increased stability against denaturant. The urea-induced unfolding monitored by the changes in fluorescence intensity at 360 nm showed that the mutation shifted midpoint of the transition from 1.9 M to 2.8 M. The mutation site is particularly interesting in that some genetic variants mapped at adjacent positions were shown previously to cause aggregation of the polypeptides, while the Phe51-->Cys mutation decreased aggregation rate significantly during heat deactivation. The association rate constant with porcine pancreatic elastase revealed that the mutation did not affect inhibitory activity significantly. The site identified may be critical for regulating stability of alpha 1-antitrypsin. Characterization of various single amino acid substitutions at position 51 suggests that volume and flexibility of hydrophobic side chain at the site are critical factors for enhancing the stability of alpha 1-antitrypsin.

Localization and therapy of human cervical tumor xenografts with radiolabeled monoclonal antibody 1H10

Murine IgG3 monoclonal antibody (Mab) 1H10, which recognizes a tumor-associated antigen expressed on the surface of more than 40% of human cervical carcinoma tissues, was used for in vivo localization and therapy of cervical tumor xenografts. A human cervical carcinoma cell line, CaSki, was used as our experimental tumor system. Mab 1H10 antigen expression on the surface of CaSki cells was found to be cell-cycle independent. The ability of Mab 1H10 F(ab')2 to bind to CaSki tumor xenografts was verified by direct immunohistochemical staining of thin tumor sections with a Mab 1H10-peroxidase conjugate. Radioimmunoscintigraphy of nude mice bearing CaSki tumors after iv administration of [131I]1H10 F(ab')2 showed clear tumor images 48 hr after Mab injection. Radiolabeled Mab 1H10 F(ab')2 was found to specifically localize in solid CaSki tumors 96 hr after antibody injection. Radioactivity in tumor tissue was 4 times higher than that in kidney tissue and over 6 times higher than that in liver tissue. Mab 1H10 F(ab')2 binding to xenografted CaSki tumors was 17 times greater than a control IgG3 F(ab')2 after 96 hr. Therapy of athymic mice bearing established CaSki tumors with three iv injections of 100 microCi [131I]1H10 F(ab')2 resulted in extensive tumor necrosis and significant suppression (p < 0.05) of tumor growth compared to that in control mice. These results indicate that Mab 1H10 F(ab')2 may be clinically useful for detection or treatment of cervical cancer.

Characterization of a human cervical carcinoma-associated antigen by lectin binding and immuno-electron microscopy

The specific binding and nature of the epitope recognized by monoclonal antibody (Mab) 1H10, which binds an antigen expressed on human cervical tumors, was characterized by enzyme digestion, lectin competition assay and immuno-electron microscopy. Membrane homogenates of CaSki cervical carcinoma cells were digested with various enzymes, then analysed by SDS-PAGE and immunoblotting. Cells grown on coverslips were treated with various enzymes and in situ binding of Mab 1H10 to cells was analysed by electron microscopy. The ability of lectin-conjugates to block Mab 1H10 binding to CaSki cells was also examined. Treatment of samples with sodium periodate abrogated antigen recognition by Mab 1H10. Neuraminidase and hyaluronidase digestion decreased but did not eliminate Mab 1H10 binding to cells in situ. Chondroitinase ABC digestion, in contrast, removed Mab 1H10 binding sites both in vitro and in situ. Trypsin and chymotrypsin digestion of cell membrane homogenates decreased the molecular weight of the Mab 1H10 antigen but did not decrease the binding intensity. Wheat germ agglutinin (WGA) strongly bound to CaSki cells and partially blocked Mab 1H10 binding, indicating that the antigen contains N-acetyl-galactosamine residues at or near the epitope recognized by Mab 1H10. Ricinus communis agglutinin (RCA) exhibited a similar binding pattern to WGA. However, concanavalin A bound only weakly to CaSki cells and was ineffective at blocking Mab 1H10 binding. The tumor-associated antigen recognized by Mab 1H10 is concluded to be a chondroitin sulphate glycoprotein or proteoglycan rather than a mucopolysaccharide or lipoprotein.

Doxorubicin: monoclonal antibody conjugate for therapy of human cervical carcinoma

Doxorubicin (Dox) was conjugated via a dextran linker to the F(ab')2 fragment of monoclonal antibody (MAb) 1H10 which recognizes an antigen expressed on the surface of human cervical carcinoma cells and tissues. Drug-antibody conjugates (1H10-Dox) with a molar ratio of Dox to MAb ranging from 40:1 to 60:1 retained antigen-binding and pharmacological activities. Anti-tumor activity of the conjugate in vitro was evaluated by measuring inhibition of [5-3H]-uridine incorporation into cellular RNA. 1H10-Dox was found to be 30 times more toxic to cervical tumor cells than a control MAb-Dox conjugate and 150 times more potent than Dox coupled to dextran. In addition, 1H10-Dox was less toxic to antigen-negative cells in vitro, suggesting that 1H10-Dox killing of cervical carcinoma cells was antibody-mediated. 125I-labeled 1H10-Dox preferentially localized in solid human cervical carcinoma xenografts in athymic mice with tumor-to-blood ratios of 1H10-Dox reaching 17.9 after 24 hr and 32.8 after 48 hr. Treatment of athymic mice bearing human cervical tumors with 1H10-Dox resulted in a dose-dependent inhibition of tumor growth. Multiple administrations of 1H10-Dox at a dose corresponding to 20 micrograms doxorubicin significantly suppressed the growth of human cervical tumors in nude mice without significant side effects (weight loss), and this suppression was antibody specific. Both i.p. and i.v. administration of 1H10-Dox were found to be equally effective. Our results suggest that 1H10-Dox may be useful for the treatment of human cervical carcinoma.

Ectopic production of prolactin in uterine cervical carcinoma

Sera from 743 patients with uterine cervical carcinoma were assayed for levels of circulating prolactin (PRL). Markedly abnormal serum prolactin levels were observed in 30.8% (229/743) of patients. During the early stages of cancer, the degree of PRL elevation in serum and incidence of abnormal PRL levels are much greater than those found for carcinoembryonic antigen, which is generally considered to be a circulating cervical tumor marker. Surgical removal of cervical carcinoma resulted in normalization of serum PRL concentrations. Immunohistochemical staining techniques and primary tissue culture of cervical carcinoma were used to verify the presence of PRL in the uterine cervical carcinoma cells. Twenty-two of forty-nine cervical carcinoma tissue sections showed cytoplasmic staining for prolactin, while normal cervix tissues tested were negative. Production of prolactin was directly demonstrated in the early tissue cultures of cervical carcinoma. These studies show ectopic production of PRL by uterine cervical carcinoma. Prolactin production may be a potential marker for detecting early occult tumors or for gauging the effectiveness of therapy for human cervical carcinoma.

Molecular properties of global suppressors of temperature-sensitive folding mutations in P22 tailspike endorhamnosidase

Two global suppressors (Val-331 greater than Ala and Ala-334 greater than Val) have been identified for temperature-sensitive folding (tsf) mutations in gene 9 of bacteriophage P22 (Mitraki, A., Fane, B., Haase-Pettingell, C., Sturtevant, J., and King, J. (1991) Science 253, 54-58). We have introduced 19 different single amino acid substitutions at the two global suppressor sites independently and examined the effects on the tailspike formation in Escherichia coli. Folding and maturation patterns of the various substitutions at the two global suppressor sites in the wild-type background suggest that Val-331 is located on the protein surface and Ala-334 is in the hydrophobic region. In combination with a tsf mutation, tsfH304 (Gly-244 greater than Arg), only Gly at 331 and Ile at 334, the substitutions that have similar side chain properties to the original suppressor sequences, were active as tsf suppressors. The newly identified suppressors of tsfH304 could also alleviate the tsf defect of three other mutations. The mutant carrying both Val-331 greater than Ala and Ala-334 greater than Val substitutions was also a global suppressor and was more active in suppressing the tsf defect than mutants carrying only one substitution. The suppressors may act by increasing the stability of an intermediate in the productive pathway of folding and maturation of the mutant polypeptides.

Therapy of human cervical carcinoma with monoclonal antibody-Pseudomonas exotoxin conjugates

Pseudomonas exotoxin A (PE) linked to the F(ab')2 fragment of 1H10, a murine monoclonal antibody recognizing a carbohydrate epitope of a glycoconjugate expressed on the surface of human cervical carcinoma tumor cells, was evaluated for in vitro and in vivo activity. PE can kill cells by ADP-ribosylating elongation factor 2 thus inhibiting protein synthesis. Disulfide- as well as thioether-linked immunotoxins (1H10-PE) killed cervical carcinoma cells in vitro and were 20-160 times more inhibitory to target than to control cells. Cell killing was antibody mediated as demonstrated by the reduction of 1H10-PE growth inhibition to target CaSki cells by free 1H10 F(ab')2. In addition, a control antibody immunotoxin was nontoxic to CaSki cells. Thioether-linked 1H10-PE administered either i.v. or i.p. suppressed the growth of established solid s.c. cervical carcinoma tumors xenografted in nude mice for over 30 days. Treatment with antibody alone or a control immunotoxin had no significant effect on tumor growth. Administration of immunotoxin i.p. was associated with less toxicity than administration i.v., but i.v. injections were more effective at suppressing the growth of established solid tumors.

Utility of the hot-wire spirometer

A comparative study has been carried out to investigate the performance of the hot-wire spirometer and the Rollingseal spirometer; the reproducibility of the data generated by an individual examiner; and the validity of data obtained by an "inexperienced examiner" using the hot-wire spirometer. The following results were obtained: 1. The experimental data given by the hot-wire spirometer were about 5-6% higher for FVC and FEV1, and about 10-12% higher for PFR, V50, and V25, respectively, when compared to the data generated by the Rollingseal spirometer. 2. The reproducibility of the data produced by the hot-wire spirometer operated by an "experienced examiner" was good, as the percent difference was about +/- 3%. 3. Reliable data were obtained with the spirometer even by an "inexperienced examiner" if he/she has gone through an on-site training concerning instrumentation and measurement methods for spirography.

New monoclonal antibody against human cervical carcinoma with diagnostic and therapeutic potential

A new murine monoclonal IgG3 antibody (Mab 1H10) was developed with specificity for human cervical carcinoma and several other tumor types. Antibody reactivity against a panel of tumor cell lines was examined by indirect immunofluorescence and quantified by flow cytometry. Mab 1H10 reacted with cervical, colorectal and bladder carcinoma cells and to a lesser extent melanoma and hepatocellular carcinoma cells but did not react with human fibroblasts, lymphocytes or RBCs. Mab 1H10, as assessed by immunohistochemical staining, bound 40/97 cervical carcinoma tissue samples, 8/16 colorectal carcinoma samples as well as a population of osteogenic sarcoma and lung, ovarian and bladder carcinoma tissues. Mab 1H10 did not react with any normal tissue or cell samples tested including cervix, ovary, breast, liver, colon, bladder, lung, spleen, cerebrum, lymphocytes or RBCs. Mab 1H10 may be useful for the targeting of drugs, toxins or radioisotopes to cervical carcinoma in humans.

Conformational stability of P22 tailspike proteins carrying temperature-sensitive folding mutations

The thermostable tailspike endorhamnosidase of Salmonella phage P22 provides a model system for comparing the role of amino acid sequences in determining the intracellular folding pathway with their role in stabilizing the mature structural protein. Complete Raman band assignments are given here for the native form of the tailspike trimer in aqueous solution. Once correctly folded and assembled, the wild-type and two well-characterized mutant proteins, tsfIle258----Leu and tsfGly323----Asp, exhibit the same secondary structure in solution, consisting predominantly of beta-strand (56 +/- 5%) and turns (17 +/- 2%). Raman bands that are sensitive indicators of hydrogen-bonding interactions of tyrosine (phenolic OH) and tryptophan (indole NH) are unchanged between 30 and 80 degrees C in both wild type and tsf mutants. Similarly, Raman bands that are sensitive to changes in the hydrophobic environment of nonpolar side chains exhibit no significant temperature dependence in wild type and tsf mutants. In contrast, these conformational features are greatly altered by chemical denaturation of the tailspike with lithium halide and guanidine hydrochloride. In the chemically denatured tailspike, the beta-strand structure is substantially converted to irregular or "random coil" conformation. These findings confirm conclusions from physiological studies that the three-dimensional structures of the tsf mutants, once stabilized at permissive temperatures, are equivalent to the native structure of the wild type, and this structure is maintained at temperatures far above those that block the folding of the chain into the final native conformation.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of the N-terminal hydrophobic sequence of hepatitis B virus surface antigen on the folding and assembly of hybrid beta-galactosidase in Escherichia coli

To investigate the mechanism of inclusion body formation and the effect of a hydrophobic sequence on the in vivo polypeptide folding, the aggregation caused by recombinant fusion beta-galactosidase in Escherichia coli was examined. Two plasmids were constructed: pTBG(H-) carried only the preS2 sequence of the hepatitis B virus surface antigen (HBsAg) in front of the beta-galactosidase gene (lacZ) while pTBG(H+) carried an additional sequence encoding the amino-terminal hydrophobic sequence of the S region of HBsAg between preS2 and lacZ. Unlike cells expressing the fusion protein not containing the hydrophobic sequence, E. coli JM109/pTBG(H+) exhibited temperature-sensitive production of beta-galactosidase. As the culture temperature increased the activity decreased dramatically. This decrease in activity was not due to a decrease in fusion polypeptide production, but rather the fusion polypeptides containing the hydrophobic sequence aggregated within the cells at high temperature. However once the fusion polypeptides folded into proper conformation at low temperature, they maintained the activity even at high temperature. The results indicate that aggregation is a consequence of incorrect folding and assembly of the polypeptides, and is not derived from the native structure. The aggregates of the pTBG(H+)-encoded fusion polypeptides did not revert to active form when the culture temperature was lowered.

Thermostability of temperature-sensitive folding mutants of the P22 tailspike protein

Temperature-sensitive folding mutations (tsf) of the thermostable P22 tailspike protein prevent the mutant polypeptide chain from reaching the native state at the higher end of the temperature range of bacterial growth (37-42 degrees C). At lower temperatures the mutant polypeptide chains fold and associate into native proteins. The melting temperatures of the purified native forms of seven different tsf mutant proteins have been determined by differential scanning calorimetry. Under conditions in which the wild type protein had a melting temperature of 88.4 degrees C, the melting temperatures of the mutant proteins were all above 82 degrees C, more than 40 degrees C higher than the temperature for expression of the folding defect. Because the folding defects were observed in vivo, the thermostability of the native protein was also examined with infected cells. Once matured at 28 degrees C, intracellular tsf mutant tailspikes remained native when the cells were transferred to 42 degrees C, a temperature that prevents newly synthesized tsf chains from folding correctly. These results confirm that the failure of tsf polypeptide chains to reach their native state is not due to a lowered stability of the native state. Such mutants differ from the class of ts mutations which render the native state thermolabile. The intracellular folding defects must reflect decreased stabilities of folding intermediates or alteration in the off-pathway steps leading to aggregation and inclusion body formation. These results indicate that the stability of a native protein within the cells is not sufficient to insure the successful folding of the newly synthesized chains into the native state.

Coat protein of potyviruses. 6. Amino acid sequences suggest watermelon mosaic virus 2 and soybean mosaic virus-N are strains of the same potyvirus

The amino acid sequence of the coat protein of watermelon mosaic virus 2 (WMV 2) was determined by a combination of peptide and nucleic acid sequencing. The coat protein of WMV 2 contained 281 amino acid residues including a single cysteine at position 132 and a blocked amino terminus. Comparison with the coat protein sequences of 20 strains of ten distinct potyviruses showed sequence homologies ranging from 43% to 69% except for the N strain of soybean mosaic virus (SMV-N), where the sequence homology with WMV 2 was 83%. This degree of homology and the location of sequence differences between WMV 2 and SMV-N is much closer to that observed between strains of the same virus than that found between distinct potyviruses. These data suggest that WMV 2 and SMV-N may be strains of the same virus.

A Mobile Oocyte Incubation Unit (MOIU): a device for improvement of the gamete intrafallopian transfer (GIFT) program

Forty couples with infertility due to various causes were selected for the gamete intrafallopian transfer (GIFT) program at our hospital. When the first 21 couples (Group A) had been treated in the program, the rate of pregnancy achieved was 23.8%, which did not seem satisfactory. This might have been caused by the distance between the embryo laboratory and the operating room. To eliminate this defect, a Mobile Oocyte Incubation Unit (MOIU) was designed. This is actually a compact laboratory that can be placed in the operating room. After the MOIU was utilized, the rate of pregnancy for the following 19 couples (Group B) increased to 42.1%. The MOIU has helped improve the performance of the GIFT program by increasing the stability of the pH value of the culture medium (Chetkowski R, et al.: J Vitro Fert Embryo Transfer 1985;2:207), lessening the exposure of the gametes to air and room temperature, and most importantly, shortening the time required for a GIFT procedure from 45-100 to 15-30 min. We expect that the MOIU will eventually become an integral part of the standard equipment for the GIFT program and make the program more successful and reliable in the treatment of infertility.

Secondary structure and thermostability of the phage P22 tailspike. XX. Analysis by Raman spectroscopy of the wild-type protein and a temperature-sensitive folding mutant

The thermostable tailspike endorhamnosidase of bacteriophage P22 has been investigated by laser Raman spectroscopy to determine the protein's secondary structure and the basis of its thermostability. The conformation of the native tailspike, determined by Raman amide I and amide III band analyses, is 52 to 61% beta-sheet, 24 to 27% alpha-helix, 15 to 21% beta-turn and 0 to 10% other structure types. The secondary structure of the wild-type tailspike, as monitored by the conformation-sensitive Raman amide bands, was stable to 80 degrees C, denatured reversibly between 80 and 90 degrees C, and irreversibly above 90 degrees C. The purified native form of a temperature-sensitive folding mutant (tsU38) contains secondary structures virtually identical to those in the wild-type in aqueous solution at physiological conditions (0.05 M-Na+ (pH 7.5], at both permissive (20 degrees C) and restrictive (40 degrees C) temperatures. This supports previous results showing that the mutational defect at 40 degrees C affects intermediates in the folding pathway rather than the native structure. At temperatures above 60 degrees C the wild-type and mutant forms were distinguishable: the reversible and irreversible denaturation thresholds were approximately 15 to 20 degrees C lower in the mutant than in the wild-type protein. The irreversible denaturation of the mutant tailspikes led to different aggregation/polymerization products from the wild-type, indicating that the mutation altered the unfolding pathway. In both cases only a small percentage of the native secondary structure was altered by irreversible thermal denaturation, indicating that the aggregated states retain considerable native structure.

Surface amino acids as sites of temperature-sensitive folding mutations in the P22 tailspike protein

Temperature-sensitive folding (tsf) mutations in the gene for the thermostable P22 tailspike interfere with the polypeptide chain folding and association pathway at restrictive temperature without altering the thermostability of the protein once correctly folded and assembled at permissive temperature. Though the native proteins matured at permissive temperature are biologically active, many of them display alterations in electrophoretic mobility. The native forms of 15 of these tsf mutant proteins have been purified and characterized. The purified proteins differed in electrophoretic mobility and isoelectric point from wild type but did not show evidence of major conformational alterations. The results suggest that the electrophoretic variations conferred by the 15 tsf amino acid substitutions are due to changes in the net charge at solvent-accessible sites in the native form of the mutant protein. During the maturation of the chains at restrictive temperature, these sites influence the conformation of intermediates in chain folding and association. The amino acid sequences at these sites resemble those found at turns in polypeptide chains. The isolation of tsf mutations requires that the mature structure of the tailspike accommodates the mutant amino acid substitution without loss of function. The solvent-accessible sites are probably at the surface of this structural protein. This would explain how bulky mutant substitutions, such as arginines for glycines, are accommodated in the native tailspike structure. Such sites, stabilizing intermediates in the folding pathway and located on the surface of the mature protein, probably represent a general class of conformational substrates for tsf mutations.

Single-mode-fiber ring dye laser

Pulsed dye-laser operation in a single-mode fiber is demonstrated by incorporating an evanescent field amplifier into an all-fiber ring resonator. Laser threshold is obtained with 60 mW of pump power. Characteristics of the vanescent fiber amplifier are investigated as functions of pump power and dye solution index.

Single amino acid substitutions influencing the folding pathway of the phage P22 tail spike endorhamnosidase

Temperature-sensitive mutations in the gene for the thermostable tail spike of phage P22 interyFere with the folding and subunit association pathway at the restrictive temperature but not with the activity or stability of the protein once matured. The local sites of these mutations and the mutant amino acid substitutions have been determined by DNA sequencing. Of 11 temperature-sensitive folding mutations, 3 were replacements of glycine residues by polar residues, and three were replacements of threonine residues by residues unable to form a side-chain H-bond. There were no proline replacements. Two of the temperature-sensitive sites in which threonine residues were replaced by isoleucine residues were homologous. These sequences probably maintain the correct local folding pathway at higher temperatures. The temperature-sensitive amino acid substitutions appear to destabilize a thermolabile intermediate in the wild-type folding pathway or to increase the rate of a competing off-pathway reaction.

Cyanobacterial phycobilisomes. Role of the linker polypeptides in the assembly of phycocyanin

The phycocyanin-containing segments of the rod substructures of Anabaena variabilis phycobilisomes consist of complexes of phycocyanin with "linker" polypeptides of 27,000 and 32,500 daltons (Yu, M.-H., Glazer, A. N., and Williams, R. C. (1981) J. Biol. Chem. 256, 13130-13136). Complexes (alpha beta)3.27,000, (alpha beta)3.32,500, (alpha beta)6.27,000, [(alpha beta)6.32,500]n, (alpha beta)6.27,000 - (alpha beta)6.32,500 were prepared, where alpha beta represents a monomer of phycocyanin, and 27,000 and 32,500 represent the 27,000- and 32,500-dalton polypeptides, respectively. Tryptic digestion of (alpha beta)3.32,500 leads to a stable (alpha beta)3.28,000 complex which does not form higher aggregates. The 32,500 polypeptide is stable to trypsin in the [(alpha beta)6.32,500]n and (alpha beta)6.27,000 - [(alpha beta)6.32,500]n=1.2 aggregates. Upon trypsin treatment of all 27,000 still assembled into higher aggregates, (alpha beta)6.21,0900 and (alpha beta)6.21,000 - (alpha beta)6.32,500. The spectroscopic properties of phycocyanin-linker polypeptide complexes were not modified by the tryptic cleavages. These results show that the 32,500 polypeptide has two distinct functional domains, a 28,000 portion necessary to the stabilization of a trimeric phycocyanin complex and a 4,500 domain which links consecutive phycocyanin hexamers in the rod substructure. The 27,000 polypeptide likewise has two distinct functional domains: a 21,000 domain stabilizes a trimeric phycocyanin complex, a 6,000 domain is exposed in all of the assembly forms examined. From these and earlier studies, it is concluded that the 6,000 domain functions in the attachment of the rod substructures to the core of the phycobilisome.

Cyanobacterial phycobilisomes. Phycocyanin assembly in the rod substructures of anabaena variabilis phycobilisomes

Phycocyanin complexes with "linker" polypeptides (Lundell, D. J., Williams, R. C., and Glazer, A. N. (1981) J. Biol. Chem. 256, 3580-3592) of 27 and 32.5 kilodaltons have been isolated from dissociated Anabaena variabilis phycobilisomes. In 0.05 M phosphate at pH 7.0, these "trimeric" complexes have the molar composition (alpha beta)3 . 27,000 and (alpha beta)3 . 32,500, where alpha and beta are the subunits of phycocyanin and 27,000 and 32,500 denote single copies of the linker polypeptides. The (alpha beta)3 . 27,000 and (alpha beta)3 . 32,500 complexes have lambda max at 638 and 629 nm and fluorescence emission maxima at 651 and 646 nm, respectively. In 0.6 M phosphate at pH 8.0, the (alpha beta)3 . 27,000 complex forms an (alpha beta)6 . 27,000 disc-shaped aggregate as seen in the electron microscope, whereas the (alpha beta)3 . 32,500 complex forms discs, (alpha beta)6 . 32,500, and stacked disc rods of varying lengths. The former material, containing the 27,000 polypeptide, when mixed with the (alpha beta)6 . 32,500 discs, limits their assembly into rods. The spectroscopic properties of the discs and rods assembled in vitro indicate that energy transfer in phycobilisome rod substructures proceeds from (alpha beta)6 . 32,500 discs to the (alpha beta)6 . 27,000 disc proximal to the core and thence to the core.

Phycoerythrins of the Red Alga Callithamnion: VARIATION IN PHYCOERYTHROBILIN AND PHYCOUROBILIN CONTENT

Phycoerythrins of several species of the higher red alga Callithamnion show virtually identical spectra, typical of R-phycoerythrins, with absorption maxima at 565, 539, and 497 nanometers. One species, Callithamnion roseum, produces a phycoerythrin lacking the peak at 539 nanometers. Comparison of a "typical" R-phycoerythrin from Callithamnion byssoides with the "atypical" phycoerythrin of C. roseum shows that both proteins carry 35 bilins per native molecule of 240,000 daltons; however, C. byssoides phycoerythrin carries 27.6 phycoerythrobilin and 7.3 phycourobilin groups, whereas C. roseum phycoerythrin carries 24.1 phycoerythrobilin and 10.9 phycourobilin groups. These differences in the relative amounts of the bilin prosthetic groups account in large measure for the differences between the absorption spectra of the native proteins. The ratio of phycoerythrobilin to phycourobilin in C. roseum phycoerythrin can be modulated by varying the light intensity during growth.Data on the physical, immunological and spectroscopic properties of Callithamnion phycoerythrins indicate that the variation in the relative number of the two bilin prosthetic groups does not affect significantly the conformation of the biliprotein.

Host-Parasite Interaction of Resistant Sugarbeet and Heterodera schachtii

The host-parasite relationships between Heterodera schachtii Schm. and the nematode-resistant diploid Beta vulgaris L. line '51501' were examined via serial sections of secondary rootlets. Second-stage larvae penetrated sugarbeet roots and migrated up to 1.95 mm before establishing permanent feeding sites. Most sedentary larvae were oriented parallel to the root axis or in various diagonal or folded positions in the cortex. Nematodes adopted no definite orientation with regard to the root apex. Nematode feeding stimulated formation of multinucleate syncytia in host tissues. Syncytia were 0.3-1.1 mm in length, up to 90 [mu]m x 150 [mu]m in cross section. Root diameters were enlarged close to feeding sites. Usually nematodes deteriorated concomitant with necrosis of syncytia, and dead nematodes frequently appeared macerated or flattened and deformed. Most nematodes did not develop to maturity" in the resistant host tissues, Cavities left by collapse of syncytia were filled by growth of parenchymatous tissue.

Fluorosis in black-tailed deer

Marked dental disfigurement and abnormal tooth wear patterns were observed in black-tailed deer (Odocoileus hemionus columbianus) taken from an area near an industrial fluoride source in northwestern Washington. Fluoride levels in the bones of these deer were from 10 to 35 times higher than levels in the bones of normal animals. These levels are similar to those associated with fluorosis of cattle.

Influence of chromosomal gene position on intragenic recombination in maize

Chromosome interchanges were used to relocate four alleles of the wx locus in order to analyze the distribution of recombination potential of the maize genome. There are two homotranslocation series: proximal, interchanges proximal to wx, thus moving the wx locus to varied positions away from a centromere; and distal, interchanges distal to wx, thereby lengthening the segment distal to wx. 1. Among the controls (homoalleles on standard chromosomes), derived from outcrosses (heterozygous sources), yield more recombination than these combinations in inbred lines. 2. All heteroallelic, homotranslocation combinations, irrespective of the extent of the locus-centromere distance, are equal or less in recombination frequency than the wx recombination in the standard chromosome. 3. Among all heteroalleles on homotranslocations, there is a positive linear correlation of inter-allelic recombination with increasing distance from a centromere but the value is always less than found in the standard chromosomes. This also is true for the same heteroallele at different positions; the longer distances show a higher recombination value than the shorter wx-centromere distance. 4. There is no effect of a lengthening distal segment on wx interallelic recombination. 5. The frequencies of Wx pollen grains arising from homoalleles on homotranslocations in most instances (except for 90/90) are not significantly different from the frequencies found with standard chromosomes. 6. The reversion frequency of the same homoallele at different positions has no relationship with the wx-centromere or wx-breakage-point distance. 7. Different homoalleles at the same position are not equally affected in wx reversion rate at the new position, although no trend is evident in wx-centromere or wx-breakage-point distance. 8. The most variation in percentage change of the Wx frequency from the controls among different heteroalleles with the same homotranslocation is found among interchanges with relatively short wx-breakage-point distances. 9. There is a significant environmental effect; the greatest change between years is among the heteroalleles with higher wx recombination. 10. Homoalleles differ from heteroalleles in response to various factors, such as wx-centromere and wx-breakage-point distances. This supports the expectation that Wx pollen grains arising from homoalleles have a different origin than do Wx pollen grains arising from heteroalleles.