Browsing by Author "WYNEKEN, U"

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    CHEMICAL MODIFICATION OF LYSYL AND CYSTEINYL RESIDUES OF YEAST RNA POLYMERASE-I
    (1981) BULL, P; ZALDIVAR, J; WYNEKEN, U; VENEGAS, A; VALENZUELA, P
    The 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.