PDBsum entry 1al3

Transcription regulation

PDB id: 1al3

Contents

Protein chain

237 a.a. *

Ligands

SO4

Waters ×253

* Residue conservation analysis

PDB id:

1al3

Name:

Transcription regulation

Title:

Cofactor binding fragment of cysb from klebsiella aerogenes

Structure:

Cys regulon transcriptional activator cysb. Chain: a. Fragment: cofactor binding fragment, residues 88 - 324. Engineered: yes

Source:

Klebsiella aerogenes. Organism_taxid: 28451. Atcc: 15380. Gene: cysb. Expressed in: escherichia coli. Expression_system_taxid: 562. Other_details: klebsiella aerogenes nctc 418. Chymotryptic c- terminal cofactor binding fragment of cysb

Biol. unit:

Tetramer (from PDB file)

Resolution:

1.80Å R-factor: 0.179 R-free: 0.246

Authors:

K.H.G.Verschueren,R.Tyrrell,A.J.Wilkinson

Key ref:

R.Tyrrell et al. (1997). The structure of the cofactor-binding fragment of the LysR family member, CysB: a familiar fold with a surprising subunit arrangement. Structure, 5, 1017-1032. PubMed id: 9309218 DOI: 10.1016/S0969-2126(97)00254-2

Date:

10-Jun-97 Release date: 24-Dec-97

Protein chain

P45600  (CYSB_KLEPN) -  HTH-type transcriptional regulator CysB from Klebsiella pneumoniae

Seq: 324 a.a.

Struc: 237 a.a.

Enzyme reactions

• Enzyme class: E.C.?

DOI no: 10.1016/S0969-2126(97)00254-2

Structure 5:1017-1032 (1997)

PubMed id: 9309218

The structure of the cofactor-binding fragment of the LysR family member, CysB: a familiar fold with a surprising subunit arrangement.

R.Tyrrell, K.H.Verschueren, E.J.Dodson, G.N.Murshudov, C.Addy, A.J.Wilkinson.

ABSTRACT

BACKGROUND: CysB is a tetrameric protein of identical subunits (M(r) = 36,000) which controls the expression of genes associated with the biosynthesis of cysteine in bacteria. CysB is both an activator and a repressor of transcription whose activity is responsive to the inducer N-acetylserine; thiosulphate and sulphide act as anti-inducers. CysB is a member of the LysR family of prokaryotic transcriptional regulatory proteins which share sequence similarities over approximately 280 residues including a putative helix-turn-helix DNA-binding motif at their N terminus. The aims of the present study were to explore further the complex molecular biology and curious ligand binding properties of CysB and to provide structural insights into the LysR family of proteins. RESULTS: The crystal structure of a dimeric chymotryptic fragment of Klebsiella aerogenes CysB comprising residues 88-324, has been solved by multiple isomorphous replacement and multi-crystal averaging and refined against data extending to 1.8 A resolution. The protein comprises two alpha/beta domains (I and II) connected by two short segments of polypeptide. The two domains enclose a cavity lined by polar sidechains, including those of two residues whose mutation is associated with constitutive expression of the cysteine regulon. A sulphate anion and a number of well ordered water molecules have been modelled into discrete electron-density peaks within this cavity. In the dimer, strands beta B from domain I and strands beta G from domain II come together so that a pair of antiparallel symmetry-related 11-stranded twisted beta-pleated sheets is formed. CONCLUSIONS: The overall structure of CysB(88-324) is strikingly similar to those of the periplasmic substrate-binding proteins. A similar fold has also been observed in the cofactor-binding domain of Lac repressor, implying a structural relationship between the Lac repressor and LysR families of proteins. In contrast to Lac repressor, in CysB the twofold axis of symmetry that relates the monomers in the dimer is perpendicular rather than parallel to the long axis of the cofactor-binding domain. This seems likely to place the DNA-binding domains at opposite extremes of the molecule possibly accounting for CysB's extended DNA footprints.

Selected figure(s)

Figure 1.
Figure 1. Schematic diagram of the CysB-binding sites (CBS) at the cysJIH, cysK cysP and cysB promoters. The boxes represent 19 base pair sequences believed to represent half-sites to which a single subunit binds [3]. At activation sites (purple), N-acetylserine stimulates CysB binding and activates transcription. N-acetylserine also stimulates binding to the accessory sites (white). N-acetylserine inhibits binding to CBS-B (red) partially relieving repression at the cysB promoter. The cofactor also diminishes binding to the accessory site CBS-K2 (green). Finally, N-acetylserine can also influence the extent of bending induced by binding at the cysK and cysP promoters. Bending at points indicated by arrows is induced by binding to both the activation site and to either half-site K2c or P3b (orange). N-acetylserine prevents binding at the latter and simultaneously stimulates binding at the activation sites. (The figure is adapted from Colyer and Kredich [27].)

The above figure is reprinted by permission from Cell Press: Structure (1997, 5, 1017-1032) copyright 1997.

Figure was selected by an automated process.