Abstract
BackgroundFamilies of paralogous oligomeric proteins are common in biology. How the specificity of assembly evolves is a fundamental question of biology. The LysR-Type Transcriptional Regulators (LTTR) form perhaps the largest family of transcriptional regulators in bacteria. Because genomes often encode many LTTR family members, it is assumed that many distinct homooligomers are formed simultaneously in the same cell without interfering with each other's activities, suggesting specificity in the interactions. However, this assumption has not been systematically tested.Methodology/Principal FindingsA negative-dominant assay with λcI repressor fusions was used to evaluate the assembly of the LTTRs in E. coli K-12. Thioredoxin (Trx)-LTTR fusions were used to challenge the homooligomeric interactions of λcI-LTTR fusions. Eight cI-LTTR fusions were challenged with twenty-eight Trx fusions. LTTRs could be divided into three classes based on their interactions with other LTTRs.Conclusions/SignificanceMultimerization of LTTRs in E. coli K-12 is mostly specific. However, under the conditions of the assay, many LTTRs interact with more than one noncognate partner. The physiological significance and physical basis for these interactions are not known.
Highlights
The LysR-Type Transcriptional Regulators (LTTRs) are a diverse family of oligomeric bacterial transcription factors
LTTRs with the ability to oligomerize as l cI repressor fusions were initially identified in a large scale screen of the E. coli genome [20]
Many showed no interactions with the l cI-LTTR fusions tested. Results of Both Grids Of the 216 potential heterotypic interactions, 37 were detected, which allowed the LTTRs to be divided into 3 classes: I) those whose Trx-LTTRs did not interact with any others, II) LTTRs whose Trx fusions formed only one or two interactions (CynR, LysR, NhaR, YneJ and YiaU), and III) LTTRs whose Trx fusions were promiscuous in their interactions with other LTTRs (Cbl, OxyR, PerR, YbeF and YdaK)
Summary
The LysR-Type Transcriptional Regulators (LTTRs) are a diverse family of oligomeric bacterial transcription factors. Identified by Henikoff et al, their number has grown to over 40,000 potential members (IPR000847 HTH_LysR) as of this writing, making it perhaps the largest family of transcriptional regulators among prokaryotes [1,2]. The LysR-Type Transcriptional Regulators (LTTR) form perhaps the largest family of transcriptional regulators in bacteria. Because genomes often encode many LTTR family members, it is assumed that many distinct homooligomers are formed simultaneously in the same cell without interfering with each other’s activities, suggesting specificity in the interactions. This assumption has not been systematically tested
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