In vitro transcription was reconstituted with HeLa cell transcription factors and RNA polymerase II, which were essentially free from DNA topoisomerase activities. DNA templates with defined negative superhelical densities were tested for transcription activity. Results of these analyses reveal that DNA superhelicity facilitates the interaction of TFIID to the fibroin gene or adenovirus major late promoter.
The results of recent studies have demonstrated the existence of sequence-directed DNA curvature in free double-stranded DNA. Curved DNAs are characterized by the periodical arrangment of short (dA) stretches on one face of the DNA helix. It can be assumed that the DNA curbature is an important determinatnt of both the function and the architecture of nucleoprotein complexes concerned in a variety of biological processes.
Liver microsomal cytochromes P450 (P450) are membrane-bound enzymes and play important roles in metabolisms of exogenous drugs and carcinogens as well as endogenous hormones. To understand the structure-function relationship of membrane-bound P450, we replaced amino acids of membrane-bound microsomal rat liver P450d with DNA recombinant technique by referring to the crystal structure of water-soluble bacterial P450cam and amino acid sequences of P450s. We reviewed here our recent results of how mutations influence the catalytic functions and spectral properties of P450d and discussed the active-site structure of P450d.
Extremely halophilic archaebacterium Halobacterium halobium cells show phototaxis to visible hight. The phototaxis requires vitamine A aldehyde, a retinal. Protein pigments containing retinal are the photoreceptors of the phototaxis. Phoborhodopsin (pR) is a photoreceptor of the negative phototaxis. Sensory rhodopsin (sR) is a photoreceptor of the positive phototaxis and S373, a transient photoproduct of sR, is another photoreceptor of the negative phototaxis. These photoreceptors are too unstable to isolate. Haloalkalophilic archaebacterium Natronobacterium pharaonis cells have pharaonis phoborhodopsin (ppR), which is also a photoreceptor of a negative phototaxis. PPR is solubilized and isolated in an active state, A methylation/demethylation system is involved in the signalling chain from photoreceptor to flagellar motor switch.
An emerging biotechnology, the evolutionary molecular engineering, provides a new design principle of functional RNAs or proteins based on the Darwinian mechanism of molecular evolution. There are three types of the evolution reactor corresponding to three types of assignment strategy between the genotype and the phenotype, namely, RNA-type, virus-type and cell-type.