LEUCINE-RESPONSIVE REGULATORY PROTEIN AND DEOXYADENOSINE METHYLASE CONTROL THE PHASE VARIATION AND EXPRESSION OF THE SFA AND DAA PILI OPERONS IN ESCHERICHIA-COLI
Mw. Vanderwoude et Da. Low, LEUCINE-RESPONSIVE REGULATORY PROTEIN AND DEOXYADENOSINE METHYLASE CONTROL THE PHASE VARIATION AND EXPRESSION OF THE SFA AND DAA PILI OPERONS IN ESCHERICHIA-COLI, Molecular microbiology, 11(4), 1994, pp. 605-618
The Escherichia coli operons daa and sfa encode F1845 and S pill, resp
ectively. In this paper we show that the expression of these operons i
s under phase variation control at a transcriptional level. The transc
ription of both operons is dependent on the global regulator leucine-r
esponsive regulatory protein (Lrp) and deoxyadenosine methylase (Dam).
Lrp is required for methylation protection of two GATC sites located
within conserved DNA sequences in the regulatory regions of these oper
ons. These GATC sites are differentially methylated, establishing a me
thylation pattern which is characteristic of either the phase ON or ph
ase OFF state. We also show that Lrp binds to the daa and sfa regulato
ry regions and that this binding is modulated by the methylation of th
e GATC sites. These results indicate that the phase variation of the d
aa and sfa operons is regulated by a mechanism involving differential
binding of Lrp owing to methylation of GATC sites in the regulatory re
gion, which is similar to the mechanism that controls phase variation
of the pap operon.