Promotor structure

Cox CD, Rinehart KL Jr, Moore ML, Cook, JC Jr (1981) Pyochelin Novel Structure of an Iron-chelating Growth Promotor for Pseudomonas aeruginosa. Proc Natl Acad Sci USA 78 4256... 

The TAFs fulfill numerous functions (Review Burley and Boeder, 1996 Struhl and Moqtaderi, 1998). On the one hand they are ascribed a structure promoting function. Some of the TAFs display a high degree of homology to the histones H2A, H3 and H4, and it is speculated that they help to create a nucleosome-like structure at the promotor. Furthermore, the TAFs are targets for protein-protein interactions with transcriptional activators. TAFs also posses enzymatic activity. TAF11250 has both a histone acetylase activity and a protein kinase activity. While the former presumable plays a role in the reorganization of the nucleosome, the latter can lead to phosphorylation of TFIIF. 

TFIIA and TFIIB support TFIID in the formation of a stable complex with the promotor. TFllB is necessary for the downstream selection of the start site for RNA polymerase 11. Interactions with TFllB ensure correct positioning of the RNA polymerase 11 on the promoter. Crystal structures have been solved for several of the intermediates of the pre-initiation complex (review Sokolev and Burley, 1997), showing, for example, that TBP affects a predominant kink in the DNA (see Fig. 1.16). TFIIB binds to the TBP-DNA complex, contacting both TBP and the DNA. 

It is expected that the activator system in the oxidic catalyst has a structure from which the right configuration is obtained on sulfiding. We feel that the promotor ions have to be... 

Asymmetric aldol-type reactions.1 This chiral diamine (1) in combination with tin(II) triflate and tributyltin fluoride (15, 314-315) effects a highly enantioselective aldol-type reaction between ketene silyl acetals and aldehydes. A tentative structure (2) has been suggested for the promotor. 

The catalytic properties of a surface are determined by its composition and structure on the atomic scale. Thus, it is not sufficient to know that a surface consists of a metal and a promoter, say iron and potassium, but it is essential to know the exact structure of the iron surface, including defects, steps, etc., as well as the exact location of the promotor atoms. Thus, from a fundamental point of view, the ultimate goal of catalyst characterization should be to look at the surface atom by atom, and under reaction conditions. At present, this is only occasionally possible in highly simplified model systems such as the well defined surfaces of single crystals, or the needle shaped tips used in field emission studies [8]. 

At the same time it was assumed that interaction of the amino groups of the silane should act as additional adhesion promotor to the polyimide surface. The use of the y-aminopropyl methyl triethoxy silane together with diepoxides (Araldite GY 266) did not improve the brittleness remarkably. The use of AMDES, however, should lead to less brittle systems due to the only two-dimensional crosslinking ability of the diethoxy silane. The basic structure formation features are given in Fig. 10. 

RNase P, which removes the 5 leader from tRNA transcripts, contains an RNA moiety in bacteria, eucarya, and archaea. The enzyme from Haloferax volcanii has been purified and the 345-nucleotide RNA portion used to generate a probe for cloning of the corresponding gene [123]. The sequence can be folded into a structure similar to that of bacterial RNase P RNAs. SI nuclease and primer extension localize the 5 end of the transcript adjacent to four potential archaeal promotor sequences. An in vitro transcript corresponding to the native RNA plus twenty 5 and nine 3 flanking nucleotides did not by itself exhibit RNase P activity (as bacterial RNase P RNAs do), under a variety of conditions. It was, however, able to reconstitute an active enzyme in combination with the protein moiety from Bacillus subtilis. This indicates that in Haloferax volcanii the RNase P RNA is the catalytic part of the enzyme but it may require some structural help [123]. 

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