Site Directed before

While the ddNs and ANPs must be converted intracellularly to their 5 -triphosphates (ddNTPs) or diphosphate derivatives before they can interact as competitive inhibitors/alternate substrates with regard to the natural substrates (dNTPs), the NNRTIs do not need any metabolic conversion to interact, noncompetitively with respect to the dNTPs, at an allosteric, non-substrate binding site of the HIV-1 RT. Through the analysis of NNRTI-resistant mutants, combined with site-directed mutagenesis studies, it has become increasingly clear which amino acid residues are involved in the interaction of the NNRTIs with HIV-1 RT, and, since the conformation of the HIV-1 RT has been resolved at 3.0 A resolution [73], it is now possible to visualize the binding site of the NNRTIs [74],... 

From such a viewpoint, we are examining primary processes of photoreactions of PYP [1] which functions as a blue light photoreceptor for a negative phototaxis of the purple sulfur bacterium Ectothiorhodospira halophila, some FP s [2] and Rh [3] by means of the fs fluorescence up-conversion measurements. In this article, we will discuss our latest results of fs fluorescence dynamics studies on PYP, because PYP is very stable for repeated irradiation which induces photocycles so that the very accurate experimental results can be obtained rather easily and also the preparation of the site-directed mutants as well as the PYP analogues with modified chromophores are rather easy. However, before that, we will summarize briefly results of our previous investigations. 

Several papers in this symposium use site-directed mutagenesis as a means of tailoring the properties of an enzyme. Today, recombinant DNA techniques are being used in many laboratories to tailor cost-effective enzyme products directed to the food industry. The technologies needed to synthesize a new gene for a new enzyme in the laboratory, attach it to an expression vector, and insert it into a microorganism are available today. It is only a matter of time before it s done. 

The regions of cytochrome b involved in the interaction with inhibitors have been identified before X-ray structures were available by the use of random or site directed mutagenesis in combination with inhibitor binding studies. It has been concluded that Qo inhibitors bind in a pocket formed by the C-terminus of helix C, the beginning of the cd... 

The importance of all the active-site groups mentioned above has been tested by site-directed mutagenesis. Before the crystal structure was available, a num-... 

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