Expression systems linkages

Fig. 12.3. Some expression systems involving noncovalent (binding) linkages. Numbers correspond to entries (methods) in Table 12.2 (5) labeling with methotrexate derivatives that recognize a dihydrofolatereductase segment, and (11) labeling with biarsenical derivatives binding to a 6-12 tetracysteine...

As a result, protein molecules can be constructed in quantities well beyond those accessible in cell-free recombinant expression systems, which incorporate residues or linkages that cannot be specified by the genetic code. Very large chimeric fusion proteins can be made, and since the reaction conditions are generally quite mild, this can be done under circumstances where the individual protein modules retain their native conformation at all... 

New sources of biocatalysts such as bovine al-3-galactosyltransferase produced by the baculovirus expression system are available and extend the vast field of enzymatic galactosylation. The enzyme transfers galactose with an a-linkage to the 3-position of the Gal residue in Fucal-2Gal 3l-OR [39]. 

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