Protein Family Models

This entry represents the N-terminal domain of XylR, an atypical AraC protein. This D-xylose-binding domain contains a periplasmic-binding protein (PBP) fold, similar to LacI/GalR transcription regulators, and mediates dimerization [1]. Paper describing PDB structure 4fe4. [1]. 23241389. Structures of the Escherichia coli transcription activator and regulator of diauxie, XylR: an AraC DNA-binding family member with a LacI/GalR ligand-binding domain. Ni L, Tonthat NK, Chinnam N, Schumacher MA;. Nucleic Acids Res. 2013;41:1998-2008. (from Pfam)

Date:

2025-01-31

This domain is found in a variety of transcriptional regulatory proteins. It is related to bacterial periplasmic binding proteins, although this domain is unlikely to be found in the periplasm. This domain acts as a sensor binding small molecule ligands that the DNA-binding domain responds to. This domain recognises Sugars, sugar phosphates, sugar acids and purines (Matilla et. al., FEMS Microbiology Reviews, fuab043, 45, 2021, 1. https://doi.org/10.1093/femsre/fuab043). (from Pfam)

Date:

2025-01-31

This domain is found in a variety of bacterial periplasmic binding proteins. This domain recognises fructose (Matilla et. al., FEMS Microbiology Reviews, fuab043, 45, 2021, 1. https://doi.org/10.1093/femsre/fuab043). (from Pfam)

Date:

2025-01-31

Date:

2025-01-31

This family includes the periplasmic binding proteins, and the LacI family transcriptional regulators. The periplasmic binding proteins are the primary receptors for chemotaxis and transport of many sugar based solutes. The LacI family of proteins consist of transcriptional regulators related to the lac repressor. In this case, generally the sugar binding domain binds a sugar which changes the DNA binding activity of the repressor domain (Pfam:PF00356). [1]. 1583688. 1.7 A X-ray structure of the periplasmic ribose receptor from Escherichia coli. Mowbray SL, Cole LB;. J Mol Biol 1992;225:155-175. [2]. 8638105. Crystal structure of the lactose operon repressor and its complexes with DNA and inducer. Lewis M, Chang G, Horton NC, Kercher MA, Pace HC, Schumacher MA, Brennan RG, Lu P;. Science 1996;271:1247-1254. (from Pfam)

Date:

2025-02-01

In the absence of arabinose, the N-terminal arm of AraC binds to the DNA binding domain (Pfam:PF00165) and helps to hold the two DNA binding domains in a relative orientation that favours DNA looping. In the presence of arabinose, the arms bind over the arabinose on the dimerisation domain, thus freeing the DNA-binding domains. The freed DNA-binding domains are then able to assume a conformation suitable for binding to the adjacent DNA sites that are utilised when AraC activates transcription, and hence AraC ceases looping the DNA when arabinose is added [1-2]. [1]. 9600836. Apo-AraC actively seeks to loop. Seabold RR, Schleif RF;. J Mol Biol 1998;278:529-538. [2]. 9600837. Arm-domain interactions in AraC. Saviola B, Seabold R, Schleif RF;. J Mol Biol 1998;278:539-548. (from Pfam)

Date:

2025-02-01

xylose operon transcription regulator XylR is a DNA transcription repressor

Date:

2018-12-13