Occurrence of a polyubiquitin structure in ubiquitin-protein conjugates

In the ubiquitin-mediated pathway for the degradation of intracellular proteins, several molecules of ubiquitin are linked to the protein substrate by amide linkages. It was noted that the number of ubiquitin-protein conjugates and their apparent molecular size are higher than expected from the number of amino groups in the protein. When the amino groups of ubiquitin were blocked by reductive methylation, it was efficiently conjugated to lysozyme, but the higher-molecular-weight conjugates were not formed. This suggests that the higher-molecular-weight conjugates with native ubiquitin contain structures in which one molecule of ubiquitin is linked to an amino group of another molecule of ubiquitin. Methylated ubiquitin stimulated protein breakdown at about one half the rate obtained with native ubiquitin, and isolated conjugates of 125I-lysozyme with methylated ubiquitin were broken down by reticulocyte extracts. These findings indicate that the formation of polyubiquitin chains is not obligatory for protein breakdown, though it may accelerate the rate of this process.

[Nuclear magnetic resonance tomography of the spine]

The present paper deals with the results of 48 MR examinations of known spinal abnormalities. The use of a method strictly related to the individual problem helps to reduce the duration of the examination. Sagittal cuts are particularly useful for demonstrating much of the spinal canal. The spin-echo method is used for all examinations. Demonstration of the cord was performed by using short repetition and echo times (TR, TE). For showing the outer margin of the spinal canal, longer TR and TE should be selected. Surface coils are important for demonstrating spinal disease, since the larger images can be performed without increasing the duration of the examination.

[Diagnosis of bone necrosis by magnetic resonance tomography. The potentials for early diagnosis]

Twenty-eight patients with necrosis in the hip joint, the femoral condyles and the talus were examined by MR tomography. This revealed various features whose frequency depended upon the various stages of the necrosis. Three patients who showed no, or only indefinite, changes on radiographs, displayed clear evidence of necrosis on MR. Staging of femoral head necrosis on the basis of MR criteria is suggested, as well as a suitable procedure for early diagnosis. Accurate localisation and knowledge of the extent of the necrosis by means of MR makes it possible to plan an osteotomy accurately.

Role of the alpha-amino group of protein in ubiquitin-mediated protein breakdown

Previous studies suggest that the conjugation of ubiquitin to NH2 groups of proteins is required for protein breakdown. We now show that the selective modification of NH2-terminal alpha-NH2 groups of globin and lysozyme prevents their degradation by the ubiquitin proteolytic system from reticulocytes. The conjugation by ubiquitin of epsilon-NH2 groups of lysine residues, usually seen in multiples, was also inhibited in alpha-NH2-blocked proteins. Naturally occurring N alpha-acetylated proteins are not degraded by the ubiquitin system at a significant rate, while their nonacetylated counterparts from other species are good substrates. This suggests that one function of N alpha-acetylation of cellular proteins is to prevent their degradation by the ubiquitin system. alpha-NH2-blocked proteins can have their activity as substrates for degradation increased by incorporation of alpha-NH2 groups through the introduction of polyalanine side chains. Proteins in which most epsilon-NH2 groups are blocked but the alpha-NH2 group is free are degraded by the ubiquitin system, but at a reduced rate. It is therefore suggested that the exposure of a free NH2 terminus of proteins is required for degradation and probably initiates the formation of ubiquitin conjugates committed for degradation.

[Concentrations and levels of activity of important serum protein components in preserved serum]

The content of transport proteins, immune globulins, components of the complement system and protease inhibitors were estimated in two different plasma preparations, using bioassays by chromogenic substrates and laser nephelometry. The content of proteins under consideration was found about 50% less than in untreated human plasma. Some proteins such as antithrombin III and factor XIII are missing. The results are discussed in respect to clinical used of plasma preparations.

ATP-dependent degradation of ubiquitin-protein conjugates

Previous studies have indicated that the ATP-requiring conjugation of ubiquitin with proteins plays a role in the energy-dependent degradation of intracellular proteins. To examine whether such conjugates are indeed intermediates in protein breakdown, conjugates of 125I-labeled lysozyme with ubiquitin were isolated and incubated with a fraction of reticulocyte extract that lacks the enzymes that carry out ubiquitin-protein conjugation. ATP markedly stimulated degradation of the lysozyme moiety of ubiquitin conjugates to products soluble in trichloroacetic acid. By contrast, free 125I-labeled lysozyme was not degraded under these conditions, unless ubiquitin and the three enzymes required for ubiquitin conjugation were supplemented. Mg2+ was absolutely required for conjugate breakdown. Of various nucleotides, only CTP replaced ATP. Nonhydrolyzable analogs of ATP were not effective. In the absence of ATP, free lysozyme is released from ubiquitin-lysozyme conjugates by isopeptidases present in the extract. Thus, ATP is involved in both the formation and the breakdown of ubiquitin-protein conjugates.

Components of ubiquitin-protein ligase system. Resolution, affinity purification, and role in protein breakdown

By affinity chromatography of a crude reticulocyte extract on ubiquitin-Sepharose, three enzymes required for the conjugation of ubiquitin with proteins have been isolated. One is the ubiquitin-activating enzyme (E1), which is covalently linked to the affinity column in the presence of ATP and can be specifically eluted with AMP and pyrophosphate (Ciechanover, A., Elias, S., Heller, H., and Hershko, A. (1982) J. Biol. Chem. 257, 2537-2542). A second enzyme, designated E2, is bound to the ubiquitin column when E1 and ATP are present, and is eluted with a thiol compound at high concentration. The third enzyme, designated E3, is adsorbed to the affinity column by noncovalent interactions and can be eluted with high salt or increased pH. The presence of all three enzymes is absolutely required for the conjugation of 125I-ubiquitin with proteins. All three affinity-purified enzymes are also required for the breakdown of 125I-albumin to acid-soluble material in the presence of ubiquitin, ATP, and the unadsorbed fraction of the affinity column. The following observations indicate that the function of E2 is the transfer of activated ubiquitin to the site of conjugation in the form of an E2-ubiquitin thiol ester intermediate. (a) E2 is rapidly inactivated by iodoacetamide, but can be protected against inactivation by a prior incubation with E1, ATP, and ubiquitin. This suggests an E1-mediated transfer of activated ubiquitin to an iodoacetamide-sensitive thiol site of E2. (b) The requirements for the binding of E2 to the ubiquitin column and the mode of its elution, cited above, are consistent with the notion that a covalent linkage is formed between E2 and Sepharose-bound ubiquitin. (c) Upon the incubation of 125I-ubiquitin with E1 and ATP, followed by the addition of purified E2, activated ubiquitin is transferred from E1 to several low molecular weight forms of E2, as analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The linkage of ubiquitin to all these forms has the characteristics of a thiol ester bond. In a further incubation with E3 and a protein substrate for conjugation, activated ubiquitin was transferred from the different forms of E2-ubiquitin to stable ubiquitin-protein conjugates. Thus, E3 is involved in the last step of the ligase system.

Gender, anxiety, and human figure drawings

Male and female human figure drawings (HFDs) produced by 340 males and females, from ages 9 yrs. 7 mos. to 22 yrs. 4 mos., and deriving from a normal population, were scored for anxiety related to aggression-hostility (A-H) and insecurity-lability (I-L). In general, male subjects evidenced more anxiety about A-H than females; additionally, both male and female subjects drew male figures with more A-H anxiety indices than female figures. The results are interpreted in terms of the impact of sex-role socialization. Further, the utility of obtaining HFDs of both sexes in personality assessment is noted.

"Covalent affinity" purification of ubiquitin-activating enzyme

We have previously described an enzyme that activates ubiquitin, the heat-stable polypeptide of the ATP-dependent proteolytic system from reticulocytes (Ciechanover, A., Heller, H., Katz-Etzion, R., and Hershko, A. (1981) Proc. Natl. Acad. Sci. U. S. A. 78, 761-765). It carries out ubiquitin-dependent PPi-ATP and AMP-ATP exchange reactions and binds to the activated polypeptide by a thiolester linkage. We describe here a procedure for the purification of this enzyme by its binding to ubiquitin-Sepharose. Binding of the enzyme to the affinity column requires ATP and Mg2+, and bound enzyme cannot be displaced by high salt but can be eluted by raising the pH, by increased concentrations of a thiol compound, or by the joint supplementation of AMP and pyrophosphate. Another form of the enzyme that cannot carry out AMP-ATP exchange (but catalyzes ubiquitin-dependent PPi-ATP exchange) does not bind to the affinity column. These data indicate that a covalent, possibly thiolester intermediate, is formed between the activating enzyme and Sepharose-bound ubiquitin. It is suggested designating this procedure of enzyme isolation "covalent affinity" chromatography. The purified enzyme has an apparent Mr = 210,000 and appears to be composed of two subunits of Mr = 105, 000. ATP-dependent binding of ubiquitin to the purified enzyme and to its subunit is demonstrated.

Activation of the heat-stable polypeptide of the ATP-dependent proteolytic system

It had been shown previously that the heat-stable polypeptide of the ATP-dependent proteolytic system of reticulocytes, designated APF-1, forms covalent conjugates with protein substrates in an ATP-requiring process. We now describe an enzyme that carries out the activation by ATP of the polypeptide with pyrophosphate displacement. The formation of AMP-polypeptide and transfer of the polypeptide to a secondary acceptor are suggested by an APF-1 requirement for ATP-PPi and ATP-AMP exchange reactions, respectively. With radiolabeled polypeptide, an ATP-dependent labeling of the enzyme was shown to be by a linkage that is acid stable but is labile to treatment with mild alkali, hydroxylamine, borohydride, or mercuric salts. It therefore appears that the AMP-polypeptide undergoes attack by an -SH group of the enzyme to form a thiolester.

Characterization of the heat-stable polypeptide of the ATP-dependent proteolytic system from reticulocytes

A heat-stable polypeptide from rabbit reticulocytes has been previously shown to be required for ATP-dependent protein breakdown (Ciechanover, A., Hod, Y., and Hershko, A. (1978) Biochem. Biophys. Res Commun. 81, 1100-1105) and to form covalent conjugates with proteins in an ATP-requiring reaction (Ciechanover, A., Heller, H., Elias, S., Haas, A.L., and Hershko, A. (1980) Proc. Natl. Acad. Sci. U.S.A. 77, 1365-1368). We now describe its purification, characterization, and tissue distribution. Its presence in erythrocytes at high level makes this a possible preferred source in the future.

Proposed role of ATP in protein breakdown: conjugation of protein with multiple chains of the polypeptide of ATP-dependent proteolysis

The heat-stable polypeptide ATP-dependent proteolysis factor 1 (APF-1) of the reticulocyte proteolytic system forms covalent compounds with proteins in an ATP-requiring reaction. APF-1 and lysozyme, a good substrate for ATP-dependent proteolysis, form multiple conjugates, as was shown by comigration of label from each upon gel electrophoresis. Multiple bands were also seen with other substrates of the ATP-dependent proteolytic system, such as globin or alpha-lactalbumin. Analysis of the ratio of APF-1 to lysozyme radioactivities and of the molecular weights of the bands indicated that they consist of increasing numbers of the APF-1 polypeptide bound to one molecule of lysozyme. The covalent linkage is probably of an isopeptide nature, because it is stable to hydroxylamine and alkali, and polylysine is able to give conjugates of APF-1. Removal of ATP after formation of the 125I-labeled APF-1 conjugates with endogenous proteins caused the regeneration of APF-1, indicating presence of an amidase. This reaction is thought to compete with proteases that may act on APF-1-protein conjugates, especially those containing several APF-1 ligands. A sequence of reactions in which the linkage of APF-1 to the substrate is followed by the proteolytic breakdown of the substrate is proposed to explain the role of ATP.

ATP-dependent conjugation of reticulocyte proteins with the polypeptide required for protein degradation

The heat-stable polypeptide (APF-1) required for ATP-dependent proteolysis in reticulocytes enters into high molecular weight conjugates upon incubation with the fraction of reticulocytes that is retained by DEAE-cellulose. Conjugate formation requires ATP and Mg2+ and its inhibited by N-ethylmaleimide. UTP and GTP are inactive. These properties are identical to those of ATP-dependent protein breakdown in the same system, suggesting that the conjugates are intermediates in this process. The APF-1 conjugates are stable in sodium dodecyl sulfate/polyacrylamide gel electrophoresis and Sephadex G-75 isolation and are resistant to mild acid, alkali, heat denaturation, and reduction; the conjugates are therefore covalent.

[Application of computer tomography (CT) as an additional means of follow-up gynecologic neoplasms-a case documentation (author's transl)]

The application of CT represents an important progress not only in diagnostic and therapeutic planning, but also in the evaluation of the effectiveness of follow-up procedures in gynecologic cancer therapy. The evaluation of the results of some follow-up procedures in a case of leiomyosarcoma uteri shows significance and importance of CT as a new radiologic method. Inspite of preliminary negative results of extensive radiologic, myelographic, laboratory investigations and of technetium- and gallium-scintigraphy, CT proved a solitary metastasis located at S-1 in the os sacrum. The diagnostic aspects of follow-up examinations in patients undergoing cytoreductive surgery or radiotherapy are discussed. CT should not be placed at first rank position, but be considered as an helpful additional means for special cases.

The influence of platelet aggregation inhibitors on metastasis formation in mice (3LL)

Platelets were suggested to play a specific role in the haematogenous spread of experimental tumours. To test this hypothesis mice were treated with various inhibitors or platelet function (acetyl-salicylic acid, RA 233, bencyclan-, cyproheptadine). The effect of treatment on the development of lung colonies after i.v. tumour cell injection as well as on the formation of spontaneous metastases from the solid Lewis-lung carcinoma was evaluated. A significant increase of lung colonies after pretreatment with the platelet aggregation inhibitors was found. The effect of long term treatment on spontaneous metastasis formation gave equivocal results. The present investigations do not support the importance of the integrity of platelet function as a prerequisite for metastasis formation.

[Ectopic course of the internal carotid artery in the tympanic cavity-value of angiography and tomography]

The rare case of an internal carotid artery crossing the tympanic cavity is reported. By means of angiography and proper positioned tomography a diagnosis can be made before any operation is attempted. A biopsy of the clinically appearing "tumor" can be disastrous for profuse arterial bleeding.

[Examination of persons in contact with plant protection and pest control agents]

It is referred to the great importance of the annual controls of farmers who work with preventive remedies for plants and insecticides. Alone during a two-year control 4-7 per cent of disabled persons and 15-18 percent who needed by all means a control were found. Among the laboratory values, apart from the quantitative determination of cholesterinase, above all the determination of the transaminases, the thymol test and the G-6-PhD stood the test. These examinations must by all means be carried out already before the beginning of the work. The number of persons who have to be controlled must be enlarged. Publications concerning other results hitherto yielded and the consequences which must be derived from this are desirable.