Tryptophan repressor (or trp repressor ) is a transcription factor involved in the management of amino acid metabolism. It is best studied by the example of E. coli , where it is a dimeric protein that regulates the transcription of 5 genes in a tryptophan operon [1] . When the amino acid tryptophan is abundant in the cell, it binds to the protein , which causes conformational changes in the protein [2]. The repressor complex then binds to its operator sequence in the genes, which it regulates by disabling the genes. [3] [4] .
| Tryptophan repressor protein | |
|---|---|
 TrpR Protein Ribbon Chart | |
| Identifiers | |
| Pfam | PF01371 |
| Pfam clan | CL0123 |
| Interpro | IPR000831 |
| SCOP | 2wrp |
| SUPERFAMILY | 2wrp |
| Available protein structures | |
| Pfam | the structure |
| PDB | RCSB PDB ; PDBe ; PDBj |
| PDBsum | 3D model |
One of the genes regulated by the Trp repressor, TRpr , encodes the tryptophan repressor protein itself. This is a form of feedback regulation.
Tryptophan repressor is a homodimer of 25 kD proteins that regulates tryptophan transcription during bacterial biosynthesis. There are 5 operons that are regulated by TRpr - trpEDCBA , TRpr , ArOH , Arol and MTR operons.
Mechanism
When the amino acid tryptophan is abundant in the cell, TRpr binds 2 molecules of tryptophan, which, therefore, changes its structure and dynamics so that it becomes able to bind to the DNA operator. When this happens, DNA transcription stops, suppressing gene products - proteins that produce tryptophan. When cell levels of tryptophan decrease, tryptophan repressor molecules break down, allowing the repressor to return to its inactive form.
TRpr also controls the regulation of its own production by regulating the TRpr gene [5] .
The structures of the limited form ligand and the free form ligand were determined in X-ray crystallography and [6] [7] [8] [9] [10] .
The trp operon consists of a regulatory gene , a promoter , an operator , and a terminator. The trp operon is active only when cellular tryptophan is insufficient. If tryptophan is lacking, the repressor protein breaks off from the operator (where the repressor usually binds) and RNA polymerase can complete its reading of the DNA strand. If RNA polymerase reaches the terminator (at the end of the DNA chain), then an enzyme for tryptophan is created.
Notes
- ↑ Santillan M., Mackey MC Dynamic regulation of the tryptophan operon: A modeling study and comparison with experimental data // Proceedings of the National Academy of Sciences of the United States of America : journal. - 2001. - Vol. 98 , no. 4 . - P. 1364-1369 . - DOI : 10.1073 / pnas.98.4.1364 . - PMID 11171956 .
- ↑ Zhang RG, Joachimiak A., Lawson CL, Schevitz RW, Otwinowski Z., Sigler PB The crystal structure of trp aporepressor at 1.8 A shows how binding tryptophan enhances DNA affinity (Eng.) // Nature: journal. - 1987. - Vol. 327 , no. 6123 . - P. 591-597 . - DOI : 10.1038 / 327591a0 . - PMID 3600756 .
- ↑ Jeeves M., Evans PD, Parslow RA, Jaseja M., Hyde EI Studies of the Escherichia coli Trp repressor binding to its five operators and to variant operator sequences (English) // Eur. J. Biochem. : journal. - 1999. - Vol. 265 , no. 3 . - P. 919-928 . - DOI : 10.1046 / j.1432-1327.1999.00792.x . - PMID 10518785 .
- ↑ Arvidson DN, Arvidson CG, Lawson CL, Miner J., Adams C., Youderian P. The tryptophan repressor sequence is highly conserved among the Enterobacteriaceae (Eng.) // Nucleic Acids Res. : journal. - 1994. - Vol. 22 , no. 10 . - P. 1821-1829 . - DOI : 10.1093 / nar / 10.22.1821 . - PMID 8208606 .
- ↑ Kelley RL, Yanofsky C. Trp aporepressor production is controlled by autogenous regulation and inefficient translation (English) // Proceedings of the National Academy of Sciences of the United States of America : journal. - 1982. - May ( vol. 79 , no. 10 ). - P. 3120-3124 . - DOI : 10.1073 / pnas.79.10.3120 . - PMID 7048301 .
- ↑ Schevitz RW, Otwinowski Z., Joachimiak A., Lawson CL, Sigler PB The three-dimensional structure of trp repressor (Eng.) // Nature. - 1985. - Vol. 317 , no. 6040 . - P. 782-786 . - DOI : 10.1038 / 317782a0 . - PMID 3903514 .
- ↑ Otwinowski Z; Schevitz RW; Zhang RG; Lawson, CL; Joachimiak, A .; Marmorstein, RQ; Luisi, BF; Sigler, PB Crystal structure of trp repressor / operator complex at atomic resolution // English : journal. - 1988. - Vol. 335 , no. 6188 . - P. 321-329 . - DOI : 10.1038 / 335321a0 . - PMID 3419502 .
- ↑ Lawson CL, Carey J. Tandem binding in crystals of a trp repressor / operator half-site complex (Eng.) // Nature: journal. - 1993. - Vol. 366 , no. 6451 . - P. 178-182 . - DOI : 10.1038 / 366178a0 . - PMID 8232559 .
- ↑ Zhao D., Arrowsmith CH, Jia X., Jardetzky O. Refined solution structures of the Escherichia coli trp holo- and aporepressor (Eng.) // J. Mol. Biol. : journal. - 1993. - Vol. 229 , no. 3 . - P. 735-746 . - DOI : 10.1006 / jmbi.1993.1076 . - PMID 8433368 .
- ↑ Zhang H; Zhao D; Revington M; Lee, W; Jia, X; Arrowsmith, C; Jardetzky, O. The solution structures of the trp repressor-operator DNA complex (Eng.) // J. Mol. Biol. : journal. - 1994. - Vol. 238 , no. 4 . - P. 592-614 . - DOI : 10.1006 / jmbi.1994.1317 . - PMID 8176748 .