Protein engineering changing specificity

Subtilisins are a group of serine proteinases that are produced by different species of bacilli. These enzymes are of considerable commercial interest because they are added to the detergents in washing powder to facilitate removal of proteinaceous stains. Numerous attempts have therefore recently been made to change by protein engineering such properties of the subtilisin molecule as its thermal stability, pH optimum, and specificity. In fact, in 1988 subtilisin mutants were the subject of the first US patent granted for an engineered protein. 

Non-excitable cells with no obvious electrical activity play the same important role as excitable cells in cell-based biosensors. The changes in electrical signals, such as cell impedance, and nonelectrical parameters such as cell morphology, proliferation, metabolism, cell viability, pH, and extracellular analyte concentrations, can be measured upon chemical exposure and physical stimuli. Cells can also be genetically engineered to express reporters or biomarkers, such as the green fluorescence protein (GFP), upon specific stimulation. 

The examples above represent some of the most successful studies in protein engineering. They show that it is possible to enhance protein thermostability rationally, alter cofactor or substrate specificity, regiospecificity, and even change catalytic activity. Furtherm ore, the creation of enzymatic activity from a non-catalytic protein backbone, and the creation of a biocatalyst with an unprecedented catalytic activity not found in nature, have also been achieved. However, the examples published in the literature are probably only a tiny fraction of the many studies that have been, or are still, in progress awaiting positive results. 

Molecular modeling is also used in protein engineering to modify specifically or randomly selected residues of a protein to change the substrate specificity or to try to find an amino acid sequence that will fold into a specific, preselected 3D shape (the inverse protein folding problem). An introduction to this topic has been written by van Gunsteren. xhe principles of modeling have also been used to design new enzymes with altered substrate specificity. - ... 

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