Operators and promoters in the OR region of phage 434.

The OR operator region of phage 434 contains three 14 bp blocks with sequence ACAAGA-A--TTGT which are presumed to be the 434 repressor recognition sites. Operator constitutive mutations are located in two of these blocks, while a mutation affecting repressor levels in the lysogenic state is located in the third. Two transcripts obtained in vitro, one leftwards and one rightwards, are tentatively identified as the Prm and PR transcription starts. the arrangement of the 434 operator region appears to be very similar to that of the OR of phage lambda.