Operons repressor

Lewis, M., et al. Crystal structure of the lactose operon repressor and its complexes with DNA and inducer. Science 271 1247-1254, 1996. 

Figure 39-2. The positional relationships of the structural and regulatory genes of the lac operon. lacZ encodes 3-galactosidase,/ocT encodes a permease, and lacA encodes a thiogalactoside transacetylase. lad encodes the lac operon repressor protein.

HTHARSR helix turn helix, Arsenical Resistance Operon Repressor AB 0(0) 0(0) 1SMT... 

HTHLACI helix turn helix lactose operon repressor B 0(0) 0(0) 1QP0... 

DOTMA E. coli E EBV ECFP ECV EGFP ELISA EYFP FACS FdG FH2 FH4 FK506 FLP propane-aminium-trifluoracetate 7V-[2,3-(dioleyloxy) propyl]-/V,/V,/V-trimethyl ammonium chloride Escherichia coli erythromycine operon/repressor Epstein-Barr virus enhanced cyan fluorescence protein extracellular viral particles enhanced green fluorescence protein enzyme-linked immunosorbent assay enhanced yellow fluorescence protein fluorescence-activated cell sorter fluorescein di- 3-D-galactopyranoside dihydrofolate tetrahydrofolate human immunophilins native recombinase isolated from the 2pm plasmid from Saccharomyces cerevisiae... 

HEK-293 hGH High-Five hsp70 HSV IPTG IRES kb Lac LCR LoxP LUC MCS human embryonic kidney cells human growth hormone TM BTI-TN-5B1-4 (cell line derived from the insect Trichoplusia ni) heat shock protein 70 herpes simplex virus isopropyl 1 -thio-fi-D-galactopyranoside internal ribosomal entry site kilobases lactose operon/repressor locus control region locus of crossover of PI luciferase isolated from firefly multiple cloning site... 

Fig. 6. Occurrence of the CXCX(4 5) CXC consensus motif. CopY, cop operon repressor protein from Enterococcus hirae Mad, transcription factor for the Ctrl copper transporter of Saccharomyces cerevisiae AMTl, transcription factor for metal-lothionein from Candida albicans ACEl, transcription factor for metallothionein from Sa. cerevisiae Grisea, MACl orthologue of Podospora anserina MT-2 p-domain, N-terminal domain of human metallothionein-2.

The simplest technique used to grow protein crystals is the batch method in which the protein is mixed with salts or other precipitants to achieve supersaturation (Fig. 2), and the vessel is sealed and set aside until crystals appear. Frequently, the supersaturation point required to induce nucleation is empirically determined by observing the onset of transient turbidity as powdered salt is progressively added to the solution. Crystals of hen egg white lysozyme used for most systematic studies of protein crystallization are grown by batch methods (Blundell and Johnson, 1976). Mouse pancreatic ribonuclease (Perry and Palmer, 1988) and the biotin operon repressor (Brennan et al., 1989) represent recent examples of use of the batch method. 

Numerous studies performed with E. coli have established that, in E. coli, biotin regulates very efficiently its biosynthetic pathway, with an absolute specificity, the biotin vitamers being inactive. As the topics has been largely reviewed, it will be only summarized here. The regulation occurs at the transcriptional level and the biotin operon repressor (BirA) has been well characterized. This 33.5 kDa bifiinctional protein is both an enzyme and a transcriptional regulator (Figure 21). It activates biotin into biotinyl-5 -AMP with ATP (reaction a) and transfers biotin on a specific lysine residue of the biotin accepting proteins (in E. coli, the biotin carboxyl carrier protein (BCCP), a subunit of acetyl-CoA carboxylase) (reaction b). When all the... 

Howard, P.K., Shaw, J. and Otsuka, A.J. (1985) Nucleotide sequence of the birA gene encoding the biotin operon repressor and biotin holoenzyme synthetase functions of Escherichia coli. Gene 35, 321-331... 

A special group of proteins called repressors control the expression of operons. Repressors are the products of regulatory genes, and the lac repressor, which is the product of the i gene, is particularly well understood. It readily aggregates to form tetramers which appear to be the active form. There are usually about 10-20 lac repressor tetramers per bacterial cell. 

The other two rate-limiting steps are catalyzed by the iron-sulfur cluster enzymes hydroxymethylbutenyldiphosphate synthase (IspG, EC 1.17.7.1/3) and hydroxymethylbutenyldiphosphate reductase (IspH, EC 1.17.1.2), which are very sensitive for oxygen damage [79]. Coexpression of the E. coli iron-sulfur cluster operon (isc), which participates in iron-sulfur cluster enzyme formation and maintenance by eliminating the isc operon repressor iscR), improved the isoprene yield [79—81]. 

The problem of recognition apparently is important both in replication and transcription, although it is rarely discussed in physical terms. The question why polymerases start and stop their action at a given point (to one nucleotide exactly ) is completely open. Recent progress in the elucidation of the sequences of RNA polymerase promotor sites shows some degree of homology between these promotors (41). There must be initiation and termination signals for all these mechanisms, as well as for their control (operon, repressor sites, etc.) (42). 

Gierer (23) had proposed palindromic structures as recognition sites for DNA-protein interactions and, specifically for operon-repressor interactions. As will be seen below, certain nucleic acid sequences in such sites are, effectively, palindromes. 

The amino acid composition of the regulator protein was studied. It possessed acid properties due to a very high content of glutamic and aspartic acids. However, this investigation still did not demonstrate that this protein itself is the operon repressor, but merely indicated that it was somehow connected with repression. 

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