Browsing by Author "ZALDIVAR, J"
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- ItemCHEMICAL MODIFICATION OF LYSYL AND CYSTEINYL RESIDUES OF YEAST RNA POLYMERASE-I(1981) BULL, P; ZALDIVAR, J; WYNEKEN, U; VENEGAS, A; VALENZUELA, PThe active site of yeast RNA polymerase I was studied using pyridoxal 5''-phosphate, p-chloromercuribenzoate and 5,5''-dithiobis (2-nitrobenzoate) as modifying agents. The enzyme was rapidly inactivated by pyridoxal 5''-phosphate, by formation of a Schiff base between the aldehyde group and lysine amino groups of the enzyme, located in the largest subunit. Out of 45 SH groups, 2 are required for enzyme activity. Since they were partially protected by substrates and DNA, they may be at the active site. A hypothetical model of catalysis is proposed based on the results presented.
- ItemDNA-POLYMERASES FROM THE EXTREMELY THERMOPHILIC BACTERIUM THERMUS-THERMOPHILUS HB-8(1985) RUTTIMANN, C; COTORAS, M; ZALDIVAR, J; VICUNA, R
- ItemINACTIVATION OF ESCHERICHIA-COLI RNA-POLYMERASE BY PYRIDOXAL 5'-PHOSPHATE - IDENTIFICATION OF A LOW PKA LYSINE AS MODIFIED RESIDUE(1975) BULL, P; ZALDIVAR, J; VENEGAS, A; MARTIAL, J; VALENZUELA, P
- ItemSUBUNITS OF YEAST RNA POLYMERASE-I INVOLVED IN INTERACTIONS WITH DNA AND NUCLEOTIDES(1978) VALENZUELA, P; BULL, P; ZALDIVAR, J; VENEGAS, A; MARTIAL, JReaction 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.