[The study of physico-chemical properties of iodinated proteins for iodine deficiency prophylaxis]

Iodine is an essential trace element, its deficiency leads to iodine-deficient diseases. Utilization of iodinated milk proteins in human diet seems to be one of possible decisions of the problem. The aim of the present work was to characterize iodinated milk proteins "Bioiod", produced by the original technology of "SPF Technovita". The presence of iodinated amino acids (mono- and di-iodotyrosine) was proved by iodinated proteins hydrolyzates HPLC--MALDI mass-spectrometry was used for the determination of iodinated proteins. The percentage of iodine incorporated into proteins was proved to be more then 2%.

Iodination of proteins in TPO transfected thyroid cancer cells is independent of NIS

This study shows that organification of radioiodide into proteins of thyroid cancer cells exogenously co-expressing the thyroid peroxidase (TPO) and the sodium/iodide symporter (NIS) is independent of NIS function. When administering (125) I to cells constitutively expressing either NIS, or TPO or NIS/TPO, next to iodide accumulation due to NIS activity, organification was exclusively observed in TPO expressing/co-expressing cells. The use of specific inhibitors for TPO and NIS showed that organification is strictly dependent of TPO and not of NIS. An identical pattern of iodoproteins migrating between approximately 75 and 200 kDa in all cell lines tested was observed. Among the five major iodoproteins, two polypeptides appear to be related and three are most probably unrelated, according to their peptide pattern. Our results significantly indicate that co-expression of TPO in NIS transfected cells mediates iodination on the one hand but on the other hand does not contribute to augmentation of a putative NIS-based radioiodide concentrator gene therapy.

Identification of iodinated proteins in cultured thyrocytes and their possible significance for thyroid hormone formation

The thyroid gland is known to generate the iodinated hormones T3 and T4 from the prohormone thyroglobulin. In this report we examined whether polypeptides other than thyroglobulin are iodinated and hormonogenic in thyrocytes and the prerequisites for their iodination. In primary cultures of porcine thyrocytes, a substantial portion of organified radioiodine was incorporated into cellular proteins other than thyroglobulin. Some of these were identified by immunoprecipitation. They included proteins of the extracellular matrix, plasma membrane proteins, and lysosomal enzymes, which follow in part a secretion and recapture pathway. All of these proteins come into contact with the iodinating system of thyrocytes located on the apical plasma membrane and possess iodination consensus sequences. Immunoprecipitation with T3- or T4-specific antibodies showed that thyroid hormones were detectable only within thyroglobulin. This was confirmed by an analysis of the iodoamino acids of thyroglobulin, cathepsin-D (representing a secretory protein), and aminopeptidase-N (a membrane-integrated protein) by two-dimensional TLC, which revealed the presence of T3 and T4 only within the polypeptide chain of thyroglobulin. These results indicate that iodoproteins other than thyroglobulin do not participate in the generation of thyroid hormones in situ.

Comparative analysis by two-dimensional iodopeptide mapping of the RhD protein and LW glycoprotein

The RhD polypeptide and LW glycoprotein were separately immunopurified with monoclonal antibodies and compared by two-dimensional (2-D) iodopeptide mapping after digestion with alpha-chymotrypsin. These proteins have distinct 2-D maps, as seen after 125I-labeling tyrosine residues (chloramine-T procedure), and even more strikingly after labeling primary amine residues (Bolton-Hunter procedure). Of the more than 20 iodopeptides visualized, only five migrated identically when preparations of RhD and LW were directly compared, suggesting that RhD and LW are different proteins that may share some common protein domains. N-glycanase treatment of the iodopeptides did not modify the 2-D map of the RhD protein but greatly affected the LW map, further indicating that LW, but not RhD, carries N-linked carbohydrate chains. After deglycosylation the LW map was different from the RhD map, confirming that the RhD and LW polypeptides are different proteins. These findings demonstrate that LW is neither a glycosylated form of Rh protein nor is Rh a precursor of LW.

In situ iodination of angiotensin-converting enzyme and other pulmonary endothelial membrane proteins

Biochemical responses of endothelial cells in culture to pharmacological or physiological stimuli are often extrapolated to define the behavior of the vascular endothelium in vivo. However, culture conditions cannot recreate the environment of endothelial cells in vivo. To compare cell functions in vivo and in vitro, we iodinated endothelial membrane proteins of both the perfused rabbit lung and cultured rabbit lung endothelial cells. Endothelial cell protein 125I-labeling in the perfused intact lung was catalyzed by lactoperoxidase and glucose oxidase immobilized on 3-10 microns polyacrylamide beads (Enzymobeads, Bio-Rad). Changes in 5-hydroxytryptamine uptake, angiotensin converting enzyme activity and perfusion pressure made before, during and/or after iodination were small, suggesting that the procedure does not grossly injury the lung. As confirmed by tissue autoradiography, iodination was confined to the vascular space. A subcellular "membrane" fraction of the whole homogenate was enriched for several iodinated proteins. Lectin binding further purified a library of putative iodinated endothelial membranes proteins, one of which was angiotensin-converting enzyme as shown by immunoprecipitation with goat anti-rabbit antibody to angiotensin-converting enzyme. Iodinated proteins of similar molecular weights were also isolated from cultured rabbit lung endothelium iodinated under the same conditions, thus confirming the endothelial lineage of proteins iodinated in the intact lung. We conclude that this technique labels endothelial surface proteins in the intact lung without causing observable tissue injury and thus should be valuable in the study of the physiology and pathophysiology of the vascular lining in vivo.

Some characteristics of soluble thyroid proteins in human fetus during morphogenesis of follicular structure

Soluble thyroid proteins of the human fetus were studied in parallel with the formation of the follicular structure of the gland using polyacrylamide disc electrophoresis and a radioimmunological method for measuring thyroglobulin (Tg). The study covered 24 fetuses obtained after sectio parvae performed at 12-28 weeks of gestation for socio-medical reasons. Before the first trimester of gestation the human fetal thyroid, which did not have an organized follicular structure contained a significant amount of the 12S protein fraction, but only trace amounts of Tg. In the cells of a gland of afollicular structure immunofluorescent material was confirmed by reaction with anti-Tg antibodies. Later, with the formation of follicles and the appearance of follicular colloid, the absolute and relative amounts of Tg in the fetal gland increased, while the 12S subunit decreased. The Tg content in the fetal thyroid was positively correlated with the total weight of the gland, i.e. gestational age. The T4 and T3 contents in Tg of human fetal thyroids (20-24 weeks) amounted to 0.54 +/- 0.39 and 0.12 +/- 0.09 mole/Tg mole, respectively. The 27 S iodoprotein was not found in any of the extracts of fetal thyroids with formed follicles and considerable amounts of follicular colloid. The finding of the 12 S protein in the human thyroid during early fetal life, i.e. in the prefollicular phase, implies a low rate of aggregation of Tg subunits (12 S). The absence of the 27 S iodoprotein from the fetal thyroid with organized follicular structure suggests the yet incomplete morphological and biochemical maturation of the fetal gland.

Cell anchorage determines whether mammary tumor virus glycoproteins are processed for plasma membranes or secretion

The subcellular localization of mouse mammary tumor virus (MMTV) glycoproteins was analyzed in infected and cloned rat hepatocarcinoma cells cultured with the MMTV transcriptional inducer dexamethasone. When reacted with protein A-coated erythrocytes in the presence of antisera specific for viral glycoproteins or with fluorescent antisera, only some of the cells acquired surface label. This diversity was dependent on cell anchorage to the substratum. In general, the more rounded, less adherent cells contained the MMTV glycoproteins on their surfaces, whereas the flatter, more adherent cells did not. After a change in adherence, a delay preceded complete remodeling of the plasma membranes. Fluorescent antibody studies of fixed cells and analyses of viral glycoprotein synthesis and shedding using L-[35S]methionine indicated that the different expression of MMTV glycoproteins in round versus flat cells is caused by a switch in posttranslational processing. In round cells, the MMTV-encoded precursor glycoprotein is proteolytically cleaved and then transported to plasma membranes as a complex of two subunits, the smaller being the membrane anchor. In flat adherent cells, the smaller subunit is rapidly degraded in an intracellular organelle and the larger is then secreted into the medium. As indicated by labeling of cells with 125I, the concentrations of several host-encoded plasma membrane components are also influenced by cell anchorage. We propose that this switch in cell surfaces and in secretions dependent upon cell-substratum attachments may be a common control mechanism important for embryogenesis, wound healing, and cancer.

Effects of TSH on iodination in rat thyroid follicles studied by autoradiography

The possible functional relation between TSH-stimulated exocytosis and TSH-stimulated iodination in the thyroid gland was studied using quantitative EM autoradiography and cytochemistry. The study was performed in rats pretreated with thyroxine for 2 days. TSH, giving i.v. 10 min before sacrifice to thyroxine-treated rats, increased organification of 125I by about 50%. TSH decreased the number of peroxidase-positive vesicles in the apical cytoplasm and increased the width of the peroxidase reaction at the apical plasma membrane, suggesting a redistribution of peroxidase. EM autoradiography after labelling with [3H]leucine showed that TSH caused a rapid redistribution by exocytosis of newly synthesized protein to the follicle lumen. The protein deposited in the lumen remained to a large extent in the microvillus region. 10 min after injection of 125I, newly iodinated protein was distributed in a gradient in the lumen periphery. TSH, given 5 min before 125I, caused a significant increase in the labelling of the colloid in the microvillus region, indicating a selective incorporation of iodine into newly synthesized molecules deposited in this region by stimulated exocytosis. Our results confirm and extend earlier observations on a functional link between exocytosis and iodination. Redistribution of peroxidase as well as newly synthesized protein to the site of iodination might be of importance.

Identification of surface membrane proteins and surface membrane antigens of plasmodium chabaudi merozoites

Surface membrane proteins of viable merozoites of Plasmodium chabaudi were iodinated by the Iodogen method and analysed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Thirteen surface membrane proteins ranging from 22 to 270 kDa were thus identified. Most of these proteins could be immunoprecipitated by sera of mice immunized with extracts of P. chabaudi. A few, however, were precipitated only by sera of mice challenged with living parasites after immunization.

Protein composition of the hyaline layer of sea urchin embryos and reaggregating cells

The protein composition of the sea urchin embryo hyaline layer has been studied by 125I surface labeling. The electrophoretic patterns of iodinated proteins indicate that the composition of the hyaline layer is species and stage-specific. Dissociation of iodinated embryos removes some labeled proteins of apparent molecular weights of 290,000, 175,000, 145,000, 110,000, 70,000, and 50,000. The electrophoretic pattern of labeled proteins found in the intact embryo is reestablished on the surface of aggregates following reaggregation. The possible function of these proteins with respect to cell adhesion, cell-sorting behavior and morphogenesis is discussed.

Characterization of human prostatic acid phosphatase radioiodinated by four different procedures

Prostatic acid phosphatase was labeled by four different iodination procedures: chloramine-T, insoluble or soluble lactoperoxidase, and Bolton-Hunter. Enzyme labeled by the chloramine-T procedure had suboptimal precipitation characteristics in immunoassays, with 36 to 67% of the tracer precipitated in antibody excess. Analysis of the tracer on 7.5% sodium dodecyl sulfate polyacrylamide gel showed that as much as 30% of the radioactivity migrated away from the protein within 6 minutes after the electrophoretic run was begun. The nature of this fast migrating radioiodinated component was not determined. The failure to obtain a tracer labeled by the chloramine-T procedure with optimal immunoprecipitation characteristics led to investigation of alternate radioiodination procedures. Insoluble or soluble lactoperoxidase was less effective than chloramine-T in producing a tracer suitable for radioimmunoassay. In contrast, the Bolton-Hunter procedure produced a tracer that had optimal precipitation characteristics; 88 to 91% of the tracer was precipitated in antibody excess. The tracer was further purified by affinity chromatography to minimize the possibility of other protein contaminants compromising the specificity of a radioimmunoassay for the enzyme.

Afrikander cattle congenital goitre--thyroglobulin-related polypeptides smaller than the half-molecule sub-units

Crude congenital goitres from cattle were enriched in iodoprotein content by gel chromatography. From this fraction thyroglobulin-like protein was isolated by affinity chromatography with antithyroglobulin IgG. The goitre thyroglobulin-like protein constituted only about 20% of the iodoprotein fraction. By analytical ultracentrifugation three boundaries were present with apparent sedimentation rates of 3S, 10,3S and 15,1S respectively. In sodium dodecylsulphate (SDS)-polyacrylamide gels only a small proportion of the reduced polypeptides of the goitre thyroglobulin-like protein co-migrated with the known half-molecules of normal thyroglobulin, while the major proportion migrated as a heterogeneous group with apparent molecular weights smaller than the half-molecules. Heavy membrane-bound polysomes were prepared from normal and goitre tissue and incubated in a reticulocyte lysate amino acid incorporating system. The translation products were isolated by specific immunoprecipitation together with carrier thyroglobulin. In SDS-polyacrylamide gels both translation products contained radioactive polypeptides which co-migrated with the half-molecules of normal thyroglobulin. The translation products obtained from the goitre polysomes, however, contained a large proportion of polypeptides which migrated faster than the half-molecule sub-units.

Direct cross-links between initiation factors 1, 2, and 3 and ribosomal proteins promoted by 2-iminothiolane

Complexes were prepared containing 30S ribosomal subunits from Escherichia coli and the three initiation factors IF1, IF2, and IF3. In different experiments, each of the factors was radiolabeled with the others unlabeled. The complexes were allowed to react with 2-iminothiolane and then oxidized to promote the formation of intermolecular disulfide bonds, some of which were between factors and ribosomal proteins. Each of the labeled factors becomes covalently cross-linked to the complex as judged by its failure to dissociate when centrifuged in a sucrose gradient containing a high salt concentration. Proteins from the complexes were extracted and analyzed on two-dimensional polyacrylamide gels by nonequilibrium isoelectric focusing and sodium dodecyl sulfate gel electrophoresis. Spots corresponding to cross-linked dimers that contained initiation factors, as indicated on autoradiographs, were cut out and analyzed further. The following cross-linked dimers between factors and ribosomal proteins were identified: IF1-S12, IF1-S18, IF2-S13, IF3-S7, IF3-S11, IF3-S13, and IF3-S19. Cross-links between factors IF1-IF2 and IF3-IF2 were also identified. A model integrating these findings with others on the protein topography of the ribosome is presented.

Biological and structural studies with an adenovirus type 2 temperature-sensitive mutant defective for uncoating

We compared some of the biological and structural features of an adenovirus type 2 temperature-sensitive mutant (ts1) defective for maturation cleavages and uncoating with wild-type (WT) virus. The cleavage defect caused ts1 to produce virions at 39 degrees that contained five precursor proteins (pTP, 11K, PVI, PVII, PVIII). Coinfection of cells with such ts1 virions and a variety of mutants or WT virus not only failed to complement ts1 but actually depressed the infection by the second virus. The uncoating defect could only be overcome by multiplicity-dependent leakiness. The structure of the ts1 virion was compared with that of WT virus by iodination with chloramine-T, chloroglycoluril and lactoperoxidase, by cross-linking, and by digestion with proteases. Aside from the presence of precursor proteins and the greater stability of ts1 virions, no other differences were found that could account for the uncoating defect. Therefore, we postulate that this defect was caused by the greater stability imparted to the virion by precursor proteins PVI, PVII and PVIII.

Abnormal iodoprotein distribution and resistance to proteolysis in Gunn rat black thyroid. An ultrastructural and biochemical study

Gunn rats have a marked deficiency in hepatic UDP-glucuronosyl transferase activity which results in hyperthyroxinemia and hyperbilirubinemia. Their thyroids show a brownish-black discoloration associated ultrastructurally with intracellular dense granules and intraluminal dense masses. In order to determine whether colloid composition and colloid proteolysis are altered in the thyroid of the Gunn rat compared with the Wistar rat, we studied the in situ resistance of thyroid proteins to in vitro proteolysis, the pattern of in vivo (125I) labeled thyroid iodoproteins and the proteolysis of isolated iodoprotein fractions in both strains of rats. For the cytochemical study, thin sections of aldehyde-fixed and plastic-embedded thyroid tissue were treated with 0.3 or 1% pronase in aqueous solution. With the low concentration of pronase, the secretory granules in C-cells and the apical vesicles in follicular cells were extensively digested in both strains of rats, whereas the colloid in the follicular lumen and the colloid droplets were only partially digested. With the high concentration of pronase, the colloid in the lumen and the colloid droplets were more markedly digested in both strains. In the presence of both concentrations of pronase, the dense granules and intraluminal dense masses were unchanged in the Gunn rats. The (125I) iodoprotein pattern was investigated 24 h after a single injection of (125I) iodide and by labeling at the isotopic equilibrium. It was found that the (125I) thyroglobulin fraction was reduced, whereas the (125I) 3-8 S fraction was increased in Gunn rats compared to Wistar rats. Pronase hydrolysis of the soluble (125I) iodine fraction showed similar pronase-resistant fractions in both strains with the single labeling procedure. At the isotopic equilibrium, the pronase resistant fraction was significantly increased in Gunn rats (Gunn 24.0 +/- 5.3%; Wistar: 13.7 +/- 3.1% of the soluble 125I) and a linear correlation was observed between the (125I) 3-8 S fraction of the soluble extract and the pronase-resistant fraction. These data suggest that iodocompounds of small molecular size and low turnover accumulate in the thyroid of the Gunn rat due to their strong resistance to in vivo hydrolysis. A local accumulation of 3-8 S iodocompounds may occur within the intracellular dense granules and intraluminal dense masses in the thyroid of Gunn rat.

Preferential secretion of triiodothyronine in man

The directly measured secretion rates of thyroxine (T4), 3,5,3'-triiodothyronine (T3), and 3,3',5'-triiodothyronine (rT3) were compared to the tissue concentrations of these hormones and to the distribution of follicular iodoproteins in 15 patients submitted to thyroid or parathyroid surgery. The T4/T3 and rT3/T3 ratios were higher for thyroid tissue than for the secretion rates, indicating a preferential secretion of T3. The concentrations of T4 and T3 were higher in the 27S iodoprotein fraction than in the 19S thyroglobulin fraction.

Variable major proteins of Borrellia hermsii

Borrelia hermsii, a relapsing fever agent, manifests antigenic variation in vivo and in vitro. We studied three mouse-passaged serotypes of strain HS1 (7, 14, and 21) and a HS1 derivative obtained after multiple in vitro passages (C serotype). All four serotypes had two major proteins in whole cell lysates fractionated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. One major protein species (pII) had the same apparent subunit molecular weight (or approximately 3.9 X 10(4) in all the serotypes. In contrast, the other abundant protein in lysates, pI, had a different apparent molecular weight in each serotype. In one gel the molecular weights of pIc, pI7, pI14, and pI21 were 1.9, 4.2, 4.1, and 4.0 X 10(4), respectively. Serotype-specific mouse antisera bound to both hemologous and heterologous pIIs, to homologous pI, but not to heterologous pI in Western blots. Hybridomas were raised from spleens of mice infected with B. hermsii. Monoclonal antibodies were identified by immunofluorescence assays using whole organisms. Monoclonal antibodies specific for serotype 7 (H1826) or for serotype 21 (H3326) bound only to pI7 or pI21, respectively, in Western blots. The surface location of the pI was suggested not only by the immunofluorescence studies but also by the labeling of pI7 and pI21 when whole cells of serotypes 7 and 21 were incubated with 125I in the presence of Iodogen. Under the same circumstances, pII was relatively poorly labeled. These studies have identified the variable pI proteins of B. hermsii as serotype-specific antigens. A change from one pI to another may be the basis of antigenic variation of Borrelia species during relapsing fever.

Thyroxine-rich iodopeptides as fragment of reduced guinea pig thyroglobulin

Full reduction of guinea pig thyroglobulin with mercaptoethanol followed by polyacrylamide gel electrophoresis reveals the presence besides the well known three polypeptide chains, of small amounts of iodopeptides with a molecular weight of 3 000 to 46 000 daltons. One of these peptides with a molecular weight of roughly 10 000 daltons has a much higher efficiency to couple iodotyrosines into thyroxine than any other fragment of thyroglobulin. Despite its small quantity this peptide contributes more than one third to the total thyroxine synthesis from a given iodide shot at any time up to five days after its injection. Iodopeptides akin to that found in guinea pigs were recently described by several authors in different species. They probably represent the preferential domains for hormone synthesis within the intact thyroglobulin molecule.

[Radioimmunoassay of plasma ferritin of Gallus domesticus L]

A new experimental procedure for chicken plasma ferritin based on the method of Luxton et al. has been carried out. All biologic reagents used were obtained in our laboratory: Ferritin from chicken liver, antiferritin antiserum from rabbits and anti-rabbit IgG from goat. Chloramine T procedure was applied to label ferritin with 125I. The iodinated protein was removed from free iodide by use of three chromatographic columns of Sephadex G-25, Sephadex G-200 and Sepharose 6B. Separation of the first antigen-antibody complex was carried out by the double antibody method. The assay working range covers from 21.8 up to 175 ng/ml. As ferritin concentration is higher in chicken plasma than in human, various plasma dilutions ranging from 1/16 to 1/64 were used.

Protein composition in single follicles, homogenates and fine-needle aspiration biopsies from normal and diseased human thyroid

The protein composition of the thyroid colloid was analysed by microgel electrophoresis and densitometry in 41 euthyroid patients. The colloid samples were obtained from single follicles by micropuncture, from homogenates of microbiopsies or from aspiration biopsies. Fourteen of the patients had morphologically normal thyroid tissue, 18 had atoxic nodular goitre and 19 of the patients had atoxic adenoma. Ten of the patients with nodular goitre had prior to the investigation received lithium therapy for psychiatric disorders. The main component of the thyroid colloid was 19S thyroglobulin (TG), but larger iodoproteins (S-TG) and smaller protein fractions, an albumin-like protein and a pre-albumin fraction, were also present in varying relative amounts. Analyses of homogenates of microbiopsies from normal thyroid tissue demonstrated the same protein composition as observed in single follicles. In colloid samples from atoxic nodular goitre the lighter protein fractions were absent in most of the samples. Analyses of homogenates or aspiration biopsies could not demonstrate this alteration in the protein composition in nodular goitre. Lithium therapy resulted in a significantly lower amount of the lighter protein fractions but unchanged amounts of the globulin fractions in atoxic nodular goitre.

Electrophoretic analysis of thyroid iodoproteins in highly cross-linked polyacrylamide gels

The electrophoretic behavior of thyroglobulin and larger thyroglobulin-like iodoproteins prepared from the hog thyroid was studied in polyacrylamide gels over a wide range of cross-linking degrees (C%). When examined at a constant total acrylamide monomer concentration (T%) of 5%, the mobility of 19S thyroglobulin decreased with increase in C below C = 5%, whereas above C = 5%, it increased markedly with increase in C, giving a minimum mobility at C = 5%. Similar biphasic mobility curves were obtained with 27S and 37S thyroid iodoproteins. Furthermore, in a region above C = 15%, at least two additional larger components which escaped detection in the gels with lower degrees of cross-linking appeared as separate bands. Ferguson plots constructed for thyroid iodoproteins at a higher constant C of 20% gave straight lines intersecting at a common point at T = 0%. From the calculated slopes of the Ferguson plots, it has been established that the thyroid contains a series of multimers of 19S thyroglobulin as constituent iodoproteins. Structural parameters of highly cross-linked gels were estimated under the assumption that the gels would be predominantly composed of a random meshwork of gel beads.

Iodination of hepatitis A virus reveals a fourth structural polypeptide

Hepatitis A virus present in the feces of two patients with naturally acquired hepatitis A was purified, radiolabeled with 125I, and analyzed by discontinuous sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In addition to the three structural polypeptides previously reported, a fourth polypeptide with a molecular weight of 14,000 was detected and shown to be a component of hepatitis A virus by immune precipitation techniques. Intact virions were also shown to sediment at 160S on sucrose gradients. These findings are consistent with hepatitis A virus being an enterovirus within the family Picornaviridae.

The membrane proteins of the vacuolar system I. Analysis of a novel method of intralysosomal iodination

A method has been developed to deliver an idoinating system into the confines of the phagolysosome, allowing us to study the nature of the phagolysosomal membrane. Lactoperoxidase (LPO) is covalently coupled to carboxylated latex spheres (LPO-latex) in a stable, enzymatically active form. The addition of LPO-latex to cultured macrophages leads to their rapid attachment, ingestion, and enclosure in a plasma membrane-derived phagocytic vacuole. These organelles rapidly fuse with preexisting lysosomes and are converted to phagolysosomes (PL) that demonstrates both acid phosphatase and lactoperoxidase activities. The exposure of LPO-latex containing cells to 125I- and an extracellular peroxide-generating system, glucose oxidase-glucose, at 4 degrees C leads to incorporation of label into TCA-precipitable material. The incorporated cel-associated label was present as monoiodotyrosine, and negligible amounts were found in lipids. Cell viability remained > 99%. Autoradiography at both the light and EM level revealed that > 97% of the cells were labeled, and quantitative analysis demonstrated the localization of grains to LPO-latex containing PL. PL were separated on sucrose gradients, and their radiolabel was confined almost exclusively to the membrane rather than soluble contents. SDS-polyacrylamide gel electrophoretic analysis of the peptides iodinated from within PL demonstrated at least 24 species with molecular weights ranging from 12,000 to 250,000. A very similar group of proteins was identified on the plasma membrane (PM) after surface iodination, and on latex phagosomes derived from iodinated PM. No novel proteins were detected in PL, either immediately after phagosome-lysosome fusion or after 1 h of intracytoplasmic residence. We conclude that the membrane proteins accessible to LPO-catalyzed iodination on the luminal surface of the PL and on the external face of the PM are similar, if not identical.

Plasma membrane polypeptides of resident and activated mouse peritoneal macrophages

With the lactoperoxidase/glucose oxidase-catalyzed iodination method, we have identified at least 19 exteriorly disposed plasma membrane polypeptides on mouse peritoneal macrophages, with molecular weights ranging from 12,000 to 290,000. Resident and inflammatory macrophages could be distinguished by qualitative and quantitative differences in the display of selected polypeptides, although the overall banding patterns were similar. Some of the labeled polypeptides were identified by immunoprecipitation.

Measurement method for radioactive thyroxine, triiodothyronine, iodide, and iodoprotein in samples with low activity

A method is described that incorporates resin extraction and thin layer chromatography to isolate and separate radioiodinated thyroxine (T4), triiodothyronine (T3), iodoprotein, and iodide in samples of human plasma up to 3 ml. Tracer studies using this method showed that reverse T3 and 3',5' diiodothyronine (T2), as well as T4, were detected in the "T4 fraction," and that 3-3' T2 and 3' monoiodothyronine, as well as T3, were detected in the "T3 fraction." Monoiodotyrosine and diiodotyrosine (DIT) migrated more slowly than did T4 on the chromatogram, and a large amount of DIT was in the unextracted "iodoprotein fraction." Kinetic studies in 14 normal subjects given intravenous commercial [125I]T3 (T3*) and [131I]T4 (T4*), confirmed the quantitative importance of an iodoprotein in later samples after T3* administration, and its presence after T4*. T4* contamination of commercial T3* also became quantitatively important. On the other hand, despite confirmation of in vivo conversion of T4* to T3*, T3* contributed little quantitatively to the total concentration of radioactivity present even late after T4* injection, due to the more rapid turnover and greater distribution volume of T3*.

Two-dimensional gel electrophoresis of 125I-labeled surface proteins of human fibroblasts

Human fibroblasts were labeled by the 125I-lactoperoxidase technique and the sodium dodecyl sulfate soluble proteins examined by two-dimensional gel electrophoresis to determine the charge heterogeneity of the surface proteins and test for differences in surface proteins in several hereditary disorders. Approximately 80 polypeptides were observed. Those below 65 000 daltons tended to occur as single spots, while those of higher molecular weight were often present as a series of polypeptides of similar molecular weight (charge isomers). The possible role of these proteins in cell-cell recognition is discussed.

Yeast plasma membrane ghosts. An analysis of proteins by two-dimensional gel electrophoresis

We have examined yeast cell ghost preparations to assess their value in obtaining plasma membrane proteins. Ghosts prepared by two methods involving stabilization of spheroplast envelopes had similar protein patterns by two-dimensional gel electrophoresis, and approximately 200 proteins were resolved. Spheroplasts were lactoperoxidase iodinated, and recovery of label in ghost preparations was greater than 60%. Spheroplasts appeared to be impermeable to the lactoperoxidase reagents as judged by an examination of two-dimensional gel electrophoretic patterns of ghost proteins that had been iodinated in spheroplasts or in unsealed ghosts. Spheroplasts were also impermeable to pronase proteases. Surface iodination and surface proteolysis allowed us to identify exposed ghost proteins; the major ghost glycoprotein was exposed in spheroplasts. Two-dimensional patterns of ghost proteins were not heavily contaminated (less than or equal to 25% of all proteins) by proteins present in soluble or promitochondrial fractions, and estimates of surface label and total cell protein recovery suggested that the ghost fraction represents a cell envelope enrichment of 8--10 fold over whole cells. Resolution of ghost proteins by two-dimensional gel electrophoresis appears to be a powerful aid toward identifying membrane proteins.

Immunochemical and immunohistochemical studies on the 27 S iodoprotein of dog thyroid with reference to thyroglobulin-like reaction of the parafollicular cells

Our earlier finding that the thyroglobulin-like material responsible for the immunoreaction of parafollicular cells obtained in peak I fraction of Bio-Gel A-5m was followed up in the present study by an investigation of the immunochemical and immunohistochemical reactions of 27 S iodoprotein which was the most prominent material in the peak I fraction. The antibody was raised against completely purified 27 S iodoprotein which was obtained as follows: Thyroglobulin was extracted from dog thyroids and chromatographed initially on Bio-Gel A-5m and then on Bio-Gel A-50m. The area of 27 S migrated as a single bank on polyacrylamide gel slab electrophoresis. This was cut and eluted. Anti-27 S antiserum showed the same immunochemical patterns to 27 S and 19 S as anti-19 S antiserum with three different immunochemical methods: double diffusion test, one dimensional and two dimensional immunoelectrophoresis. The immunoperoxidase reactions of the anti-27 S antiserum and anti-19 S antiserum were restricted to follicular cells and luminal colloids. No reaction of the parafollicular cells was obtained by these antisera. Thus, 27 S iodoprotein shared common immunochemical and immunohistochemical properties with 19 S thyroglobulin. It was concluded that 27 S iodoprotein was not responsible for the thyroglobulin-like reaction of the parafollicular cells.

Subunit structure of 27 S thyroid iodoprotein

The dissociation of thyroid 27 S iodoprotein by sodium dodecyl sulfate (SDS) and by succinic anhydride was investigated by means of ultracentrifugation and polyacrylamide gel electrophoresis. The iodoprotein obtained from either a human or hog was dissociated into three kinds of subunits (S-19, S-17 and S-12) by SDS treatment. At increased concentrations of SDS, the S-12 subunit was predominant among the dissociation products. The succinylation of 27 S iodoprotein showed essentially the same dissociation pattern as in the case of SDS treatment. The dissociation products of the protein preparations of different animals were qualitatively the same as those of thyroglobulin of the respective animals, confirming the hypothesis that 27 S iodoprotein was composed of two molecules of thyroglobulin. However, the extent of dissociation of 27 S iodoprotein measured by S-12 formation showed higher resistancy of the protein to the dissociating agents than that of thyroglobulin. The contents of sialic acid and hexose as well as iodoamino acids of 27 S iodoprotein were found to be the same as, or not far from, those of thyroglobulin. The dissociability and chemical composition of 27 S iodoprotein was discussed with reference to the subunit structure of the protein.

Evaluation by electron microscopy of the integrity of iodinated plasmalipoproteins

Iodination of proteins and lipoproteins is a widely used "in vitro" labelling procedure in metabolic, autoradiographic and various other studies. However, all available iodination techniques have involved the possible damage to the proteins by self-irradiation, oxidizing agents, the alkaline milieu or by the introduction of iodine into the molecular structure itself. To evaluate the integrity of iodinated lipoprotiens, we observed the electron microscopic appearance of normal and iodinated rabbit very low density lipoproteins (VLDL) by negative staining with phosphotungstic acid. Iodination up to a molar iodine/protein ratio of 2.89 did not results in any change of shape, size or aggregating tendency of the particles. No stacks or disk-like particles like those of various hyperlipoproteinemic states were found. We conclude that electron microscopy is a valuable tool in assessing the morphological appearance of lipoprotein iodination, but it should be complemented by other techniques.

Preparation of 125I-labeled synthetic porcine secretin for radioimmunoassay

Synthetic porcine secretion was labelled by the conjugation-labelling method of Bolton & Hunter, the lactoperoxidase method, the gaseous diffusion method, and the chloramine-T method. The chloramine-T technique was adapted as routine method. Ten mug (3.27 nmol) peptide was reacted with 5 mCi of Na125I at a concentration of chloramine-T of 1.3 mmol/l. Synthetic secretin was suitable for labelling for at least eight months when stored as dry matter in nitrogen-filled glass ampoules. Purification and separation of labelled from unlabelled hormone was carried out by gel-permeation chromatography on Sephadex G-50 superfine. The labelled preparation had a specific radioactivity of 405 +/- 33 muCi/nmol (mean +/- SEM., n = 9) and was unable for six days. 6-tyrosyl-secretin took more iodine compared to porcine synthetic secretin but had lower immunoreactivity with all antisera tested.

Subunit structure of 27 S thyroid iodoprotein

The dissociation of thyroid 27 S iodoprotein by sodium dodecyl sulfate (SDS) and by succinic anhydride was investigated by means of ultracentrifugation and polyacrylamide gel electrophoresis. The iodoprotein obtained from either a human or hog was dissociated into three kinds of subunits (S-19, S-17 and S-12) by SDS treatment. At increased concentrations of SDS, the S-12 subunit was predominant among the dissociation products. The succinylation of 27 S iodoprotein showed essentially the same dissociation pattern as in the case of SDS treatment. This dissociation products of the protein preparations of different animals were qualitatively the same as those of thyroglobulin of the respective animals, confirming the hypothesis that 27 S iodoprotein was composed of two molecules of thyroglobulin. However, the extent of dissociation of 27 S iodoprotein measured by S-12 formation showed higher resistancy of the protein to the dissociating agents than that of thyroglobulin. The contents of sialic acid and hexose as well as iodoamino acids of 27 S iodoprotein were found to be the same as, or not far from, those of thyroglobulin; The dissociability and chemical composition of 27 S iodoprotein was discussed with reference to the subunit structure of the protein.

9 S thyroid particulate iodoprotein

Particulate iodoproteins have been studied in the rat thyroid gland using the isotopic 125I equilibration method. Pulse experiments were also performed with a second isotope, 131I. Labelled iodoproteins, both soluble and solubilized by digitonin from the thyroid particulate material, were analyzed by sucrose-gradient ultracentrifugation. 1. At isotopic equilibrium and irrespective of the iodide content of the diet two particulate iodoproteins, with sedimentation coefficients of 27 and 19 S, were solubilized by digitonin. In addition a 9 S iodoprotein was also present but its proportion varied markedly with the iodine content of the diet: it accounted for 50-60% of the label found at the particulate level when the dialy diet of iodine was high (75-500 mug/day) but was almost absent when the diet was only 2 mug/day. 2. Most of this 9 S protein was found in the 600-15 000 times g particulate pellet, i.e. a fraction enriched in lysosomes and phagolysosomes. 3. The iodoamino acid composition of the 9 S fraction was very similar to that of the 19 S particulate thyroglobulin: its hormone content was 19%. 4. The double precipitation technique showed that the 9 S fraction is immunochemically related to thyroglobulin. 5. Pulse experiments showed that the 9 S particulate iodoprotein was slowly labelled by 131I. 6. The amount of 9 S iodoprotein was increased by thyrotropin (30-40% increase versus control experiments 5 min after thyrotropin injection). These properties of the 9 S particulate iodoprotein are discussed in relation to the assumption that it might be a product of partial proteolysis of thyroglobulin after endocytosis and partial digestion by the phagolysosomes.

The structure and properties of 27S and larger iodoproteins in the thyroid gland

Iodoproteins larger than 19S were isolated from hog and calf thyroid glands using gel filtration on Sepharose 6B and one or two centrifugations in glycerol density gradients. Purified protein fractions were analysed in the analytical ultracentrifuge and characterized by the combined use of electrophoresis in continuous polyacrylamide gel gradients and electron microscopy. Three bands migrating more slowly than 19S could be identified in the polyacrylamide gels. Electron microscopy of the fastest of these species, having a sedimentation constant of 27S, showed pairs of 19S thyroglobulin molecules which had the same size and the same ovoid shape as normal, well-iodinated thyroglobulin molecules. The ovoids were randomly attached side to side, end to end. The more slowly migrating proteins were shown to consist of similar aggregates of three, four or more randomly attached molecules. Iodine and sialic acid determinations in 27S and 19S separated from the same pool of well iodinated protein showed no difference in iodine content but a larger amount of sialic acid in 27S than in 19S.

[Utraviolet adsorption and fluorescence of human thyroalbumin]

Some spectral properties of human thyroalbumin have been studied. Ultra-violet absorption of the aqueous solution of this protein has two maxima: at the wavelengths of 276 and 296--298 nm. Under the excitation by a monochromatic light with the wavelength of 280 nm the thyroalbumin has the fluorescence spectrum with the maximum at 430 nm and the quantum yeild of fluorescence about 5,4%. It has been established that thyroalbumin fluorescence consists of two components with the maxima at 385 and 450 nm. Moreover the "sortwave" component is principally attributed for by the presence do iodoamino acids.

[Study on correlations between certain biological parameters and the Achillean reflexogram in a homogeneous African population (author's transl)]

Study of a homogenous population comprising 25 male Africans. The following parameters have been measured: proteinemia, hematocrit, natremia, calcemia, globular and plasmatic magnesemia, duration of the achillean reflexogram. Hyperproteidemia and hypomagnesemia, which are usually observed in African people, were found. A negative linear relationship significant at the 10 0/0 threshhold has been demonstrated between the reflexogram and the P.B.I. value.

[Value of separation on ion exchange resins of plasma iodine fractions. Comparison with Werner's suppression test]

This was a study of 71 patients suspected of hyperthyroidism who had undergone a tri-iodothyronine suppression test. A study of circulating protein-bound iodine after separation on ion-exchange resins had been carried out before triiodothyronine administration, on the same patients. The results showed that the radioactive hormonal fraction has a better diagnostic value than radioactive serum protein-bound iodine. In 60% of cases, a study of the radioactive hormonal fraction could have permitted to avoid the use of the suppression test.