Browsing by Author "MARTIAL, J"

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    SUBUNITS OF YEAST RNA POLYMERASE-I INVOLVED IN INTERACTIONS WITH DNA AND NUCLEOTIDES
    (1978) VALENZUELA, P; BULL, P; ZALDIVAR, J; VENEGAS, A; MARTIAL, J
    Reaction of yeast [Saccharomyces cerevisiae] RNA polymerase I with pyridoxal 5''-phosphate and sodium borohydride under conditions which inactivate the enzyme results in the specific binding of pyridoxal 5''-phosphate to subunits of 185,000, 137,000, 48,000 and 36,000 daltons. Nucleotides, which protect the enzyme from inactivation specifically inhibit the binding of pyridoxal 5''-phosphate to subunits of 185,000 and 137,000 daltons. DNA which also protects the enzyme from inactivation by pyridoxal 5''-phosphate prevents the binding of the reagent to the 4 polypeptides. These results suggest that subunits of 185,000 and 137,000 are involved in interactions with both nucleotides and DNA presumably of the type leading to initiation and/or polymerization and that subunits of 48,000 and 36,000 daltons also bind to DNA but this interaction is not strictly required for polymerase activity.
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    THE PH-DEPENDENCE OF RAT-LIVER RNA POLYMERASE-I AND POLYMERASE-II
    (1980) BULL, P; MARTIAL, J; TELLEZ, R; VENEGAS, A; VALENZUELA, P
    The effect of pH on the stability and activity of rat liver RNA polymerases I (A) and II (B) was studied. Both enzymes are irreversibly inactivated in buffer solutions below pH 5.0. Km values of the 2 enzymes are constant between pH 6.5 and 8.7, but a 2- to 3-fold increase is observed between pH 8.7 and 9.7. The Vmax vs. pH profiles are bell-shaped curves indicating the participation of 2 ionizing groups with apparent pKa values of 6.5 and 9.8 for enzyme I and 6.7 and 9.9 for enzyme II. Both enzymes are inactivated by photooxidation in the presence of Rose Bengal. The above pKa corresponds to the imidazole of a histidine residue and an amino group of a lysine residue.