Open AccessSpacer mutations in the lac ps promoter.
Author(s) -
James E. Stefano,
Jay D. Gralla
Publication year - 1982
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.79.4.1069
Subject(s) - base pair , promoter , biology , dna , base (topology) , genetics , homology (biology) , rna polymerase , microbiology and biotechnology , rna , gene , mathematics , gene expression , mathematical analysis
Mutations have been constructed that delete either one or two base pairs near position -19 in the lac ps promoter. Deletion of either of two adjacent base pairs increases the rates of open complex formation by nearly on order of magnitude. Two promoters that have different single-base deletions are indistinguishable by either their rates of open complex formation or stability of the open complexes once formed. However, simultaneous deletion of both base pairs produces a promoter that forms complexes at a rate similar to that of the unmodified DNA sequence. The maximal rate of open complex formation is achieved at a spacer length of 17 base pairs, the most frequently occurring spacer length among promoters. These results suggest that the spacing between the two strongly conserved regions of sequence homology is an important determinant of the rate of open complex formation. A model is suggested that proposes that three important promoter elements, the -10 region, the -35 region, and the spacer region, act simultaneously to facilitate open complex formation by RNA polymerase.