Role of the N-terminal region and of beta-sheet residue Thr29 on the activity of the omega(2) global regulator from the broad-host range Streptococcus pyogenes plasmid pSM19035

Item Type:	Article
Title:	Role of the N-terminal region and of beta-sheet residue Thr29 on the activity of the omega(2) global regulator from the broad-host range Streptococcus pyogenes plasmid pSM19035
Creators Name:	Welfle, K. and Pratto, F. and Misselwitz, R. and Behlke, J. and Alonso, J.C. and Welfle, H.
Abstract:	The dimeric regulatory protein wild-type {omega} (wt {omega}2) binds to arrays of 7-bp sequences (heptads) present in the operator DNA region of copy control and partition functions of plasmid pSM19035. Each {omega}2 protein probably binds with an antiparallel {beta}-sheet structure in the major groove of the 7-bp subsite of the operator DNA. Exchange of threonine at position 29 to alanine (T29A) drastically affects the activity of variant protein {omega}2T29A both in vivo and in vitro, and reduces the thermodynamic stability {delta}G u 0, but does not change the conformation. Likewise, the binding affinity to DNA is reduced and the association of the two monomeric subunits of the {omega}2T29A dimer is weakened, as manifested by an increase in the dissociation constant from 3.2 {my}M for wt {omega}2 to 6.3 {my}M for {omega}2T29A. Denatured dimers are formed upon thermal unfolding of wt {omega}2 and {omega}2T29A at ca. 45 {my}M (D n↔D u). Removal of 8 ({omega}2{delta}N8), or even 18 ({omega}2{delta}N18) N-terminal amino acids has no obvious effect either on the core structure or on the activity in comparison to wt {omega}2. The stability of variants {omega}2{delta}N8 and {omega}2{delta}N18 is similar to that of wt {omega}2, and their binding to operator DNA is not impaired.
Keywords:	MetJ/Arc Superfamily, Protein-DNA, Interaction, Protein Folding, Thermodynamics, Transcriptional Repressor
Source:	Biological Chemistry
ISSN:	1431-6730
Publisher:	de Gruyter
Volume:	386
Number:	9
Page Range:	881-894
Date:	1 September 2005
Official Publication:	https://doi.org/10.1515/BC.2005.103
PubMed:	View item in PubMed

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