Chemical structure of a modification of the Escherichia coli ribonucleic acid polymerase alpha polypeptides induced by bacteriophage T4 infection.

The cr-polypeptides of Escherichia coli RNA polymerase are known to be chemically modified within 4 min after infection by bacteriophage Tq. This paper reports a crude system derived from T1-infected E. coli which will modify the cr-polypeptides of purified E. coli RNA polymerase in vitro. The product of this in vitro reaction is identical with the modified (Y found in viva ; it differs chemically from the “altered” a! observed after Tq infection in the presence of chloramphenicol. The in vitro reaction is rapid, being 50% complete within 30 s at 37”; the enzyme activity responsible appears less than 2 min after infection at 30”. These data on kinetics of synthesis and activity are consistent with data on kinetics of cr modification in vivo. Specifically labeled radioactive substrates have been used in this in vitro modification reaction to investigate the chemical substitution introduced during a! modification. The chemical stability of the modification and the sequence of pronase peptides containing the modified region of (Y also have been examined to complement the information obtained with the in Vitro system. Modification involves covalent attachment of 1 adenine nucleotide, apparently adenosine diphosphoribose, to a specific arginine in the ol-polypeptide at the sequence Thr-Val-Arg. NAD+ serves as the donor of this nucleotide in the in vitro reaction. The a modification is hypothesized to involve adenosine diphosphoribose linked through its terminal ribose to a guanido nitrogen of arginine.