U Becker

Max Planck Institute of Biochemistry, München, Bavaria, Germany

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Publications (18)29.56 Total impact

  • H Rohde, U Becker, H Nowack, R Timpl
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    ABSTRACT: Antibodies to calf or sheep skin procollagen, to its consitituent pα1(I) and pα2 chain or to peptide fragments from the aminoterminal region in pα1(I) were studied by radioimmune assays using various 1250-labeled antigens. The highest antibody response was obtained against the globular region in pα1(I). The adjacent precursor-specific collagenous and non-helical domains may modulate the antigenicity of the globular determinants but are themselves only weak antigens. No antigenic determinants were detected in the pα2 chain. Antibodies to pα1(I) chain did not cross-react with pα2 or pα1(III) chains.Antisera against the globular procollagen peptide showed no difference between the peptide and procollagen indicating that the release of the globular region from pα1(I) by collagenase is not accompanied by large conformational alterations. Complete cross-reaction was observed between precursor-specific peptides obtained from calf or sheep procollagen. Reduction and S-carboxymethylation of the five disulfide bridges in the globular region largely destroyed antigenicity. However, a minor fraction of the antibodies against the native peptide could still react with the unfolded peptide.Determinants recognized in this reaction are apparently shared by the native and unfolded peptide and were stable towards trypsin. On the other hand, antibodies prepared against the reduced and alkylated procollagen peptide did not react with the native peptide.The data indicate that that globular regions in pα1(I) chain possesses both conformational and sequential determinants which differ considerably in their immunogenic capacity.
    Immunochemistry 01/1977; 13(12):967-74.
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    ABSTRACT: A collagenous peptide T1X was isolated from a tryptic digest of the insoluble matrix of calf skin. The peptide consists of two identical polypeptide chains each with a length of 72 amino acid residues joined by a cross-link. Absorption spectra obtained from hydrazone and azine derivatives of T1X indicated that the peptide contains an aldol-type of cross-link (X). The sequence of 23 amino acid residues in the amino-terminal region was determined as Glx-Tyr-Glu-Ala-Tyr-Asp-Val-X-Ser-Gly-Val-Ala-Gly-Gly-Gly-Ile-Ala-Gly-Tyr-Hyp-Gly-Pro-Ala. This sequence overlaps the previously described amino-terminal sequence of alpha1 (III) chain obtained from pepsin treated, insoluble type III collagen. Thus, the present data demonstrate a nonhelical segment of 14 amino acid residues in type III collagen important for cross-linking.
    Hoppe-Seyler's Zeitschrift für physiologische Chemie 01/1977; 357(10):1409-15.
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    U Becker, H Nowack, S Gay, R Timpl
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    ABSTRACT: A cross-linked fragment (peptide T1X) with a molecular weight of 13,000 could be isolated from a tryptic digest of insoluble type III collagen of calf skin. Peptide T1X was conjugated on to bovine serum albumin by glutaraldehyde and used for immunization of rabbits. The antisera reacted in passive haemagglutination and radioimmune assay with peptide T1X, type III collagen and its constituent alpha1(III) chain. Little or no reaction was observed with type I collagen and alpha1(I) chain. While rabbit antisera to neutral salt-soluble type III Collagen also showed a strong binding for 125I-labelled peptide T1X much less reaction was observed with antisera to type I collagen. The antigenicity of type III collagen was largely destroyed by pepsin treatment suggesting that it resided in non-helical segments. A fragment of peptide T1X produced by digestion with collagenase retained antigenic activity. The data indicated that the aminoterminal region of type III collagen contains strong antigenic determinants located in a non-helical sequence of about sixteen amino acids. Antibodies to these antigenic determinants were purified and rendered specific for type III collagen by immunoadsorption. The antibodies stained in indirect immunofluorescence tests particularly those regions in various connective tissues which are rich in reticulin fibres. Different staining patterns were observed with antibodies to type I collagen.
    Immunology 08/1976; 31(1):57-65. · 3.71 Impact Factor
  • H Rohde, H Nowack, U Becker, R Timpl
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    ABSTRACT: Peptides derived from the aminoterminal portion of the palpha1(I)-chain of calf and sheep procollagen were labeled with iodine-125. Despite changes in electrophoretic homogeneity after labeling, reaction of the labeled peptide with antisera to unlabeled peptide was retained. Antisera to procollagen or the isolated procollagen peptide showed high titers for the native peptide, a much weaker binding with the reduced and alkylated peptide and little or no reaction with collagen. Antisera to collagen showed strong binding with collagen and a weaker but distinct reaction with the procollagen peptide. Evidence was obtained that a minor contaminant of procollagen peptide was present in the acid-extracted collagen and that there were no shared antigenic determinants. Bovine serum and amniotic fluid contained 1-10 mug/ml reactive antigen. These results indicate that the labeled peptides can be used as a specific, sensitive and accurate assay for the amino-terminal portion of procollagen in biological samples.
    Journal of Immunological Methods 02/1976; 11(2):135-45. · 2.23 Impact Factor
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    ABSTRACT: Antibodies to bovine type I and type III collagen and their precursor form procollagen were produced in rabbits and rendered specific for the immunizing antigen by immunoadsorption. These purified antibodies showed distinct immunofluorescence staining on frozen sections of both bovine and human connective tissue at concentrations as low as 1–10 μg/ml. Antibodies to type III collagen and procollagen reacted with reticulin in liver and spleen, with fascicles around tendons and with the upper portion of the dermis. Antibodies to type I collagen and procollagen reacted with skin and fiber bundles in tendon but did not stain reticulin. No reaction was observed with cartilage collagen or with kidney glomerular basement membrane.
    Journal of Immunological Methods 02/1976; · 2.23 Impact Factor
  • Biochemistry - BIOCHEMISTRY-USA. 01/1976; 15(13):2853-2862.
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    ABSTRACT: Peptides derived from the aminoterminal portion of the pα1(I)-chain of calf and sheep procollagen were labeled with iodine-125. Despite changes in electrophoretic homogeneity after labeling, reaction of the labeled peptide with antisera to unlabeled peptide was retained. Antisera to procollagen or the isolated procollagen peptide showed high titers for the native peptide, a much weaker binding with the reduced and alkylated peptide and little or no reaction with collagen. Antisera to collagen showed strong binding with collagen and a weaker but distinct reaction with the procollagen peptide. Evidence was obtained that a minor contaminant of procollagen peptide was present in the acid-extracted collagen and that there were no shared antigenic determinants. Bovine serum and amniotic fluid contained 1–10 μg/ml reactive antigen. These results indicate that the labeled peptides can be used as a specific, sensitive and accurate assay for the amino-terminal portion of procollagen in biological samples.
    Journal of Immunological Methods. 01/1976;
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    ABSTRACT: Non-helical peptide fragments were isolated from rabbit skin collagen after cleavage of alpha chains with cyanogen bromide and proteases. Determination of their amino acid sequence indicated a length of 9, 16 and 25 amino acid residues for the non-helical sequences located in the N-terminal region of alpha2 and alpha1 chain and in the C-terminal region of alpha1 chain, respectively. The C-terminal sequence Tyr-Tyr hitherto considered as the genuine end of collagen alpha1 chain is in part of rabbit collagen extended by two residues, alanine and arginine. Rabbit collagen may differ considerably in its non-helical sequences from other vertebrate collagens, particularly in the C-terminal part. Some but not all of these differences are clustered in areas occupied by antigenic determinants which are recognized in the antibody response of rabbits to rat or calf collagen. On the other hand, a high homology to rabbit collagen, e.g. in the N-terminal region of rat collagen alpha1 chain or calf collagen alpha2 chain, probably prevents immunological recognition by the rabbit. The degree of foreignness alone, however, may not necessarily determine whether a particular non-helical area is able to express immunogenic activity.
    European Journal of Biochemistry 07/1975; 54(2):359-66. · 3.58 Impact Factor
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    R Gollwitzer, U Becker, R Timpl
    FEBS Letters 11/1974; 47(1):177-80. · 3.58 Impact Factor
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    FEBS Letters 12/1973; 36(3):281-4. · 3.58 Impact Factor
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    U Becker, R Timpl
    FEBS letters 11/1972; 27(1):85-88. · 3.54 Impact Factor
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    ABSTRACT: Chicken antibodies to native rat skin collagen reacted with the random-coiled α1- and α2-polypeptide chains in gel precipitation and passive hemagglutination. The chains were not equivalent in their serologic specificity. They could not be distinguished from α-chains derived from pronase-treated collagen which lacks short, terminal sequences. The antibodies reacted with all of the large cyanogen bromide peptides obtained from the α-chains. Evidence is provided that each of these peptides carries unique antigenic determinants not found at other sites of the molecule. Complete serologic identity or strong cross-reactions were observed between α-chains obtained from different rat tissues or from other species. The results suggested that these antigenic determinants are conformation independent and are located in amino acid sequences of the helical part of the collagen molecule, known to be of high evolutionary stability. The more variable, non-helical sequences in the terminal positions of the chains were not involved. These findings are discussed in relation to the quite different specificity reported for rabbit antibodies to rat collagen.
    Immunochemistry 09/1972; 9(8):789-98.
  • European Journal of Biochemistry 09/1972; 28(4):497-506. · 3.58 Impact Factor
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    ABSTRACT: The , β and chains were isolated from reduced and carboxymethylated bovine fibrinogen by chromatography on CM-cellulose. Electrophoretically pure polypeptide chains could be obtained as judged by three different methods. The chains were soluble in buffers at or above pH 8 but exhibited non-covalent aggregation. The molecular weights of the , β and chains were estimated in dodecylsulfate-polyacrylamide gel electrophoresis as 62000, 58000 and 48000, respectively. Each chain differed considerably from the other in amino acid composition as well as in the fragment pattern obtained after CNBr treatment. The occurrence of unresolved /β material suggested microheterogeneity of the individual chains. Sulfitolysis yielded, at least for the chain, less pure products.Between 20% and 54% of the antibodies in rabbit antisera to native fibrinogen precipitated with the and/or β chain. Absorption studies, gel precipitation and hemagglutination-inhibition suggested a considerable antigenic homology of both chains. They could be clearly distinguished from the chain which reacted poorly in precipitation test but considerably better in passive hemagglutination. Cyanogen bromide cleavage did not destroy the serologic activity of the chains. These findings indicated that a considerable number of the antigenic determinants on fibrinogen are not dependent on intact conformation. However, antibodies specifically reacting with the native molecule occur as well.
    European Journal of Biochemistry. 07/1972; 28(4):497 - 506.
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    Udo Becker, Rupert Timpl, Klaus Kühn
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    ABSTRACT: The prevalent antibody response in the rabbit to acid-soluble calf collagen is specifically directed to sites on the C-terminal cyanogen bromide peptides 1-CB6a, 1-CB61b and 2-CB (3.5). Three different antigenic determinants each unique for one of these peptides could be defined serologically. After tryptic cleavage of 1-CB6a or 1-CB6b the full serologic activity was found on peptides composed of 39 and 28 amino acid residues, respectively. The center of the antigenic determinants could be located around a tyrosine residue in the nonhelical sequence of these peptides. Chymotrypsin which cleaved at this point completely abolished the serologic activity. Evidence is provided that 1-CB6b is derived from 1-CB6a by loss of 18 amino acid residues from the C-terminal end. Therefore, the antigenic determinant on 1-CB6b might be artificially created by tissue proteases. During this process a loss of activity for the antigenic determinant on 1-CB6a was observed. Extraction of the collagen polypeptide chains with 8M urea prevented this degradation and revealed in comparison to 1-CB6a an additional C-terminal tyrosine residue.
    European Journal of Biochemistry. 06/1972; 28(2):221 - 231.
  • FEBS letters 04/1972; 21(1):75-79. · 3.54 Impact Factor
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    Febs Letters - FEBS LETT. 01/1972; 21(1):75-79.
  • Immunochemistry. 10/1970; 7(10):876–877.