caa a22 4500 469090855 CHVBK 20180323133016.0 cr unu---uuuuu 170328e19920501xx s 000 0 eng 10.1007/BF00419751 doi (NATIONALLICENCE)springer-10.1007/BF00419751 Specific regulatory role of phosphorylation of calf thymus DNA-topoisomerase I smaller forms on the relaxational activity expression [Elektronische Daten] Phosphorylation role on Topo I smaller forms activity [S. Coderoni, M. Paparelli, G. Gianfranceschi] Calf thymus Topo I is found to be associated with three active breakdown products, resolved from intact enzyme, which do not appear to be unique to one extraction procedure. They are phosphoproteins, whose enzymatic activity can be modulated through changes in phosphorylation, and which can be phosphorylated ‘in vitro', by N II protein kinase, in the same five sites as the intact enzyme. Different amounts of 32P incorporated are observed however, in the corresponding sites. We conclude: 1. Proteolysis is probably an ‘in vivo' phenomenon, as the Topo I smaller species are observed, during isolation from the earlier crude fractions, and as a minimum of them is always present, even if precautions are taken to minimize proteolysis; 2. a specific regulatory role in the DNA relaxational activity might be played by N II protein kinase phosphorylation, indeed, in the smaller species; 3. the different degrees of 32P incorporation, in analogous phosphorylation sites, might represent a different signal for modulating the gene expression. Kluwer Academic Publishers, 1992 activity regulation nationallicence phosphorylation nationallicence Topo I smaller forms nationallicence CIAP : calf intestinal alkaline phosphatase nationallicence DDT : dithiotreitol nationallicence PAGE : polyacrylamide gel electropheresis nationallicence PMSF : phenyl methane sulfonyl fluoride nationallicence SDS : sodium dodecyl sulfate nationallicence Topo I : Topoisomerase I nationallicence Coderoni S. Department of Molecular Cellular and Animal Biology, University of Camerino, 62032, Camerino, (MC), Italy aut Paparelli M. Department of Molecular Cellular and Animal Biology, University of Camerino, 62032, Camerino, (MC), Italy aut Gianfranceschi G. Institute of Cellular Biology, University of Perugia, Perugia, Italy aut Molecular Biology Reports Kluwer Academic Publishers 16/2(1992-05-01), 75-80 0301-4851 16:2<75 1992 16 11033 https://doi.org/10.1007/BF00419751 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00419751 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Coderoni S. Department of Molecular Cellular and Animal Biology, University of Camerino, 62032, Camerino, (MC), Italy aut NATIONALLICENCE 700 1- Paparelli M. Department of Molecular Cellular and Animal Biology, University of Camerino, 62032, Camerino, (MC), Italy aut NATIONALLICENCE 700 1- Gianfranceschi G. Institute of Cellular Biology, University of Perugia, Perugia, Italy aut NATIONALLICENCE 773 0- Molecular Biology Reports Kluwer Academic Publishers 16/2(1992-05-01), 75-80 0301-4851 16:2<75 1992 16 11033 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer